Saturday, March 30, 2019

Twenty Years a Bruin

Table of Contents

1. Introduction
2. Accommodations
3. Barry Garelick
4. Music Class
5. Spring Break Mocha Music
6. New Xenharmonic Wiki
7. Coding Kite Colors in Mocha
8. Operation Varsity Blues
9. Bruce William Smith
10. Conclusion

Introduction

Today's second spring break post will consist of a hodgepodge of recent topics that I started to discuss in old posts but I never had time to return to until now. It also involves a reference to one topic that I intentionally saved until spring break.

The title of this post, "Twenty Years a Bruin," refers to the fact that today is the 20th anniversary of the day I received my fat envelope in the mail informing me that I'd been admitted to UCLA.

Accommodations

I try to avoid writing on the blog about the accommodations granted to special ed students. Many of these accommodations are of a personal or sensitive nature, and these students and their families wouldn't want me posting their accommodations on a blog.

But there is one recent accommodation that I want to discuss today, only because it reveals a flaw in my classroom management style. So of course, I want to post as little identifying information about this accommodation as possible.

Here are the only details that I wish to reveal on the blog:
  • The accommodation was granted at some point during this calendar year. I waited until spring break to post it to make it more difficult to trace.
  • The accommodation was granted at one of the two districts I where I sub. It might be the district that's already on spring break, or it might be the one that's still in "Big March" mode.
  • I don't reveal the gender of the student receiving the accommodation. I'd rather use the ungrammatical singular "they" than give away the gender.
  • The student themself isn't aware that they're receiving the accommodation. (Yes, "themself" is even less grammatical than singular "they.")
  • I don't reveal what the accommodation is. All that matters for this post is that the student must be in their assigned seat in order to receive the accommodation.
And on the day that I subbed in that classroom, I was able to grant the accommodation to the student without incident. So why am I blogging about it at all? Consider the following imaginary scenario.

I enter a classroom and am supposed to grant an accommodation to a student. The student must be in their assigned seat in order to receive the accommodation. But when the student enters the classroom, they go to a seat other than their assigned seat, preventing me from granting the accommodation.

I tell the student to go to their correct seat. But then one of their friends say, "How juvenile! Only kindergarten teachers make their students sit in assigned seats. All our other middle/high school teachers let us sit wherever we want, just like college professors."

I tell the student to go to their correct seat again. This time, the student themself asks, "Why do I have to sit over there?"

"So I can give you the accommodation" I reply truthfully.

"You're not supposed to talk about our accommodations openly!" the student complains.

And that's not what I want to have happen, yet this is what I fear if this scenario were to occur if I'm the regular teacher.

To seasoned teachers, it's obvious what I should have done in this fictional situation. The only correct answer to the question "Why do I have to sit over there?" is "Because I said so." And if the student refuses to sit in the assigned seat, then I punish them for defiance -- not for avoiding accommodation.

This scenario never happened at my old charter school, but of course it could have. Back then, it never occurred to me to answer "Because I said so" -- I hated that phrase when I was a young student, and so I never wanted to give that phrase as an answer.

But as I know now, there are many times when it's better for the students not to know the reason behind an unpopular rule. In this case, seating charts allow the teacher to conceal accommodations -- always from the other students, sometimes even from the accommodated student themself.

Even though this never happened to me at the old charter school, something similar to this scenario really did happen to me as a student teacher. (This was back before I started blogging, and the student at the time was a junior/senior and is now an adult, so I see no harm in blogging the accommodation.)

In this case, my master teacher was telling me about accommodations. One girl needed to sit near the front of the room so she can hear the lessons better. My master teacher told me to have this girl switch seats with another student -- she insisted that I be the one to tell both of them to move, so that I could practice giving my students directions.

But the two students refused to move. I then told the other student that I needed to accommodate an unspecified student -- but the original girl easily figured out that I was referring to her. That was when she complained about my talking about her accommodation.

Of course, many students talked loudly in my student teaching class all the time. There were these two guys who, according to my master teacher, needed to be separated. (This has nothing to do with any accommodations -- it was just to keep them quiet.) But every time she separated them, one would ask me to let him sit next to the other for the day. Since he asked for permission, I would allow him to move, thus undermining the master teacher's efforts to keep them apart.

Now imagine all of this from the perspective of the accommodated girl. She was probably wondering why it was so important for her to be quiet and sit in another seat when these two boys could move and talk whenever they wanted. She might even had suspected it was because I was sexist.

In order for me to fulfill accommodations effectively, I need to be a strong classroom manager, so that accommodation can fit smoothly into a classroom where students generally listen to, obey, and respect the teacher. "Because I said so!" needs to be my answer to any question regarding why the students need to obey me, since the truth might be that my directions are to give accommodations that I should not reveal.

Barry Garelick

This post is labeled as traditionalists, because Barry Garelick is back to posting. His blog entry dated Thursday is mostly a link to an article he writes for another site, so I'll just link directly to his article:

https://truthinamericaneducation.com/education-reform/various-narratives-growth-mindsets-and-an-intro-to-one-of-my-parole-officers/

Notice that Truth in American Education is mostly an anti-Common Core website, so it's logical that Garelick would write articles for them. OK, let's proceed:

If you are reading this, you either have never heard of me and are curious, or you have heard of me and have pretty much bought into my “narrative” of math education.

You wish, Barry! I've heard of you, but I haven't bought into your narrative at all. I do agree with some of what Garelick and the other traditionalists write, but obviously not everything.

I’m currently teaching seventh and eighth grade math at a K-8 Catholic school in a small town in California. Prior to that, I taught seventh and eighth grade math for two years at a K-8 public school in another small town in California, which is where I will start this particular narrative.

So far this "narrative" is interesting. I knew that Garelick is a California middle school math teacher, but I didn't know that it's at a Catholic school. I do recall some of what he wrote about his prior student teaching, which is what this narrative is all about.

But now he muses about why he had to leave his old district:

Specifically teachers like me who choose to teach using explicit instruction; who use Mary Dolciani’s 1962 algebra textbook in lieu of the official one; who believe that understanding does not always have to be achieved before learning a procedure; who post the names of students achieving the top three test scores;

Posting the top three test scores reminds me of the data wall I had at the old charter school. But I'm not quite sure what exactly that has to do with traditionalism, since our old Illinois State text is as far from traditional as you can get.

who answer students’ questions rather playing “read my mind” type of games in the attempt to get them to discover the answer themselves, and attain “deep understanding”.

This is a tricky one. What exactly does Garelick mean by "answer students' questions"? For example, suppose a student asks "What's the answer to Question #30?" Simply telling the student the answer doesn't lead to increased student learning -- it's just bailing out a lazy student. Therefore when I'm asked this question, sometimes I do try to get students to discover or work out the answer themselves.

This also reminds me of another traditionalist complaint -- when we make students explain their answers or show all their work. Sometimes this is the only way we can tell that a student isn't cheating on the test. Thus Garelick forgets that there are students who are lazy, cheating, or looking for ways to get credit without knowing any math.

For example, I once told my latest eighth grade algebra class that my classroom is one place where they won’t hear the words “growth mindset”—to which the class reacted with loud applause. The current educationist narrative interprets “growth mindset” (wrongly, in my opinion) as building confidence in oneself which then leads to engagement which breeds motivation and ultimately success.

And here we go again with "growth mindset." It's surprising that traditionalists would find a "growth mindset" to be so objectionable. The opposite of a "growth mindset" is a "fixed mindset" -- the idea that mathematical intelligence is fixed. It's the idea that some people are good at math and others are bad at math, and that nothing will make a bad math student into a good math student -- not even do traditional p-sets. Indeed, students who believe in a "fixed mindset" are very likely to leave most traditional p-sets blank. It's only because of a "growth mindset" that students can do anything at all to grow from being bad at math to being good at math -- whether that something is traditional or not.

Notice that Garelick does say that "growth mindset" has been interpreted wrongly. Presumably he believes that there is a correct interpretation of "growth mindset" -- one that at least allows students to grow from "bad at math" to "good at math" by doing traditional p-sets.

Garelick now describes a conversation between himself and his master teacher (or more precisely, his "induction mentor"):

“Students should do math not only in the classroom, but outside; give examples of real world problems. Many students dislike math because they find it irrelevant.” As a final proof to this statement she added that it is common for adults to say:”What on earth did I learn algebra for?”

Anyway, here's Garelick's punchline, when someone tells him the following:

“You must know this. Your students love you. They tell me that they really learned a lot about math and that you were the best math teacher they ever had.”

Once again, since Garelick is describing living, breathing students, I must take him at his word. I have indeed seen evidence that while a majority of students don't necessarily enjoy traditional math, they aren't quite as enthusiastic about reform math as the reformers.

I notice that once again, Garelick has posted an article dated March 31st -- yet I can see it on my computer today, March 30th. I'll try to get in the habit of waiting to comment on such "post-dated" (or Greenwich-dated) posts until after that reaching that date in the Pacific time zone. This gives more time for him to receive additional comments, which I can then mention in my post.)

Spring Break Music

It is spring break in my old district whose calendar is observed on the blog. But in my new district from which I get the lion's share of subbing assignments, it is not spring break. In fact, I subbed in four classrooms this week, from Tuesday to Friday.

The first class was a eighth grade math class. I was almost guaranteed to sub in a math class on Tuesday, since that was the day the Math Performance Tasks were graded. So the one day I knew I'd be in a math class in one district just had to fall during spring break in the other district, making it into a non-posting day. I'll write a little about the class today, but not "A Day in the Life."

(Last year, I wrote that I might make a "spring break" post when I subbed for math in the other district, but this year I didn't post it. I wanted to make that special post about the Easter date and didn't want to post again so soon.)

Three of the classes were Common Core 8 and the other two were Algebra I. Fortunately, you already know what these classes are learning from last week's post -- angles and parallel lines in Math 8 and factoring in Algebra I.

Oh, and by the way, in the two Algebra I classes, one student in each class was a seventh grader. I asked the two guys what math class they'll take next year. Actually, they're not quite sure -- one of them said he might take Geometry at the district office while the other might take it online.

The next two days were both science at the same middle school. Many of the same students in Tuesday's math class were also in this science class. Once again, I was reminded about my science failures at the old charter school -- especially since this district, just like my old charter, uses only an online textbook. So these classes show me what my own science lessons could have looked like if I had taught them correctly.

In these classes, seventh graders are currently learning about photosynthesis and cellular respiration while eighth graders are studying evolution. The seventh graders in one of the classes even got to watch some videos by Bill Nye the Science Guy.

Oh, and sorry Garelick -- one of the science teachers told me not to answer student questions directly, but to get them to figure out the answers themselves. (You should be glad it wasn't the math teacher!)

Yesterday, my final class of the week, was in a high school music class. You know what that means -- this is now going to be a Mocha music post as I try to convert some of the songs I heard yesterday into computer format.

I know -- I often post music during vacation posts anyway. Eight days ago I mentioned music only to discuss the Johann Sebastian Bach Google Doodle. This time, it's back to Mocha. But first, let me describe the classes.

Second period was Guitar, while the remaining classes were all vocalists. The guitarists prepared for a test next week. I've decided to convert the guitar music into Mocha today.

In two of the vocal music classes, the students will be going on a trip to New York in two weeks to perform at on the most famous musical stage in the country -- Carnegie Hall. But as we all know from the riddle, the only way to get to Carnegie Hall is to practice. And that's exactly what the singers in third and sixth do. In New York, they'll perform is Spiritual Potpourri -- as the name implies, it's actually a combination of four songs, "Do Lord," "Walk Together Children," "A City Called Heaven," and "Old Time Religion." They practiced the first two of these songs yesterday.

As we learned last week with the Bach doodle, music is typically divided into four parts -- soprano, alto, tenor, and bass. But actually, one of the classes -- third period -- was only for girls, and thus there were only the soprano and alto parts. In sixth period, all four parts were present. The singers divided into parts, with each part practicing in a different room.

In both classes, the sopranos were the ones to remain in the choir room with me. As we also found out with the Bach doodle, the soprano section typically contains the melody of the song (the part that a soloist would sing). The highest note that these sopranos sang was a" (or A5), which is the second A above middle C. This note -- also the highest playable note on the Bach doodle -- is Degree 48 (Sound 213) in Mocha.

Fourth and fifth periods didn't have a performance to prepare for. Instead, these students get to have a "talent show" day -- some of them come up to the front of the room and sing their own song. Like third period, fifth period consisted of all girls, while fourth period was co-educational.

The first duo to perform was two guys who sang an original tune. The topic of the song was their Biology class -- "Punnett Squares" This of course reminded me of the songs I sang at the old charter during music break -- and this inspired me to sing those songs that day in class. I didn't bring my music book to the classroom, but I rushed to my car to grab the book before fifth period began.

One girl in fourth period also performed two songs. Both of them come from The Lion Guard -- a spin-off series based on Disney's The Lion King. One of the songs has a title in Swahili -- "Zuka Zama," which means "pop up and dive in." As I mentioned on the blog last year in another post, Swahili is the language spoken in the movie Lion King -- many catchphrases ("Hakuna Matata") and even character names (Simba, "lion") come from that language.

When fifth period began, I had my book of songs ready. This class was smaller than fourth period and these girls were less willing to perform. Thus I gave them an incentive -- each time a girl performed, I'd perform a tune from my book. Just as I did at the old charter school, I played the songs on a guitar, since there are so many guitars in the classroom.

Here are the songs I played yesterday:
  • U-N-I-T Rate (parody of UCLA fight song)
  • Ghost of a Chance (Square One TV parody of Michael Jackson's "Thriller")
  • Measures of Center Song (parody of "Row Row Row Your Boat")
  • No Drens (parody of TLC's "No Scrubs")
  • All About That Base and Height (parody of Meghan Trainor's "All About That Bass")
  • Big March (parody of "The Ants Go Marching")
Of course I had to sing the UCLA fight song parody yesterday, since today is the anniversary of the day I became a Bruin.

Notice that all of these songs are parodies. I assumed that my most popular songs are versions of tunes that they already know, and so I intentionally chose these songs as an incentive. This includes the Measures of Center Song (an extra tune I played while waiting for a girl to perform) and the Big March Song (which I played since in this district, we are indeed still in the Big March).

Eventually, all the girls performed as the entire class sang the song "Joshua," which is all about the Biblical Battle of Jericho.

Even though sixth period already had their own songs to sing for Carnegie Hall, I couldn't help but sing one more song for them, just as all four groups were returning to the choir room right at the end of the period. Since it was a science song that started it all, I played my science song -- "Earth, Moon, and Sun," a parody of "Hava Nagila." That's right -- even my science song was a parody, and I ended up singing basically all of my parodies yesterday.

Spring Break Mocha Music

Let's get back to second period Guitar class. The songs that I'll convert to Mocha today are the spiritual "Peace Like a River" and the round "Scotland's Burning."

Both of these songs are in the key of A major. The students are playing rhythm guitar, where they learn how to strum the chords. The songs contain the three main chords in this key -- A, D, E7.

Of course, for Mocha we're not coding the chords -- we're coding the melody. Fortunately for us, neither melody contains the full A major scale. "Peace Like a River" is pentatonic -- it contains only five notes, namely A, B, C#, E, F#.

And "Scotland's Burning" is even easier as it contains only four notes -- A, B, C#, E. This makes the song Fischinger playable -- referring to the Fischinger Google Doodle, which was the last musical doodle before the Bach one.

Then again, the Fischinger doodle contained only four bars while "Scotland's Burning" has eight. But we can take advantage of the song's structure as a four-part round (similar to Kristin Lawrence's "Ghost of John" from Halloween). On the Fischinger player, we code all four parts to play at the same time. Actually, the first and fourth parts are identical, so only three parts are coded. Since each part is two bars, we repeat it twice to fill the four bars. As the Fischinger player loops, it sort of sounds like a multi-part round.

I'm not quite sure how the round is played in the actual Guitar class. I asked a few students, who inform me that the class hadn't reached that song yet. The song repeats only the E7 and A chords in each part, and so the four parts would sound identical in the classroom unless they are switching to lead guitar (where the melody is played) instead of rhythm guitar.

But that's enough about Fischinger and the guitar -- we're trying to play these songs in Mocha. We've coded pentatonic scales in Mocha before, but those weren't based on simple EDL scales (instead we searched for all of the "white," or Pythagorean, notes in Mocha).

The simplest EDL containing five notes is 10EDL. But unfortunately, while four of the notes fit a major pentatonic scale (1/1 tonic, 10/9 major 2nd, 5/4 major 3rd, 5/3 major 6th), the perfect fifth is missing from 10EDL. In its place we a have 10/7 tritone.

Our most promising EDL for anything resembling a major scale is 18EDL. This scale also contains four of the five pentatonic notes (1/1 tonic, 9/8 major 2nd, 9/7 supermajor 3rd, 3/2 perfect 5th). But fortunately, the lack of a major 6th is is irrelevant for "Scotland's Burning," which doesn't even contain the sixth.

As for "Peace Like a River," our only available sixth is the 18/11 neutral 6th. Fortunately, the sixth only appears in this song as eighth notes, so the difference between the sixths are less noticeable.

Both songs span an octave, but the span is from fifth-to-fifth, not tonic-to-tonic. Therefore the version of the scale we'll use for both songs is:

Degree  Note            Function
12          white A       perfect fifth
11          lavender B  neutral sixth ("Peace" only)
10          green C       not used in either song
9            white D       tonic
8            white E       major second
7            red F#         supermajor third
6            white A       perfect fifth ("Scotland" only)

Here white D is the tonic, not white A. But due to our span, the scale ends up turning into 12EDL rather than 18EDL. So far, I've never thought of using 12EDL in this manner -- a no-fives version of the major pentatonic scale starting on the perfect fifth. (Here "no-fives" means that the only multiple of five, namely the 10, has been omitted.)

It's possible to use the basic 10EDL/20EDL framework for "Peace Like a River." Instead of a perfect fifth, we use the wide fifth 20/13. Like the sixth, the fifth only appears as eighth notes. But these eighth notes are consecutive, so it's easier to hear the defect here than with the neutral sixth above. I thus recommend that we use 12EDL for both songs. (And 13 for the fifth is completely unacceptable for "Scotland," which needs the fifth in the higher octave.)

Let's code the songs now. First is "Peace Like a River."


10 FOR V=1 TO 3
70 N=1
80 FOR X=1 TO 48
90 READ A,T
100 SOUND 261-N*A,T
110 NEXT X
120 DATA 7,2,8,2,9,4,9,2,9,2,9,2,7,2
130 DATA 8,2,9,2,9,4,9,2,9,2,11,2,12,2
140 DATA 12,2,11,2,9,4,9,2,9,2,7,2,7,2
150 DATA 8,2,9,2,8,12
160 DATA 7,2,8,2,9,4,9,2,9,2,9,2,7,2
170 DATA 8,2,9,2,9,4,9,2,9,2,11,2,12,2
180 DATA 12,2,11,2,9,4,9,2,9,2,7,2,7,2
190 DATA 8,2,8,2,9,12
200 RESTORE
210 NEXT V

Don't forget to click on the "Sound" button. The song repeats thrice as there are three verses:

First Verse:
I've got peace like a river,
I've got peace like a river,
I've got peace like a river in my soul;
I've got peace like a river,
I've got peace like a river,
I've got peace like a river in my soul.

Second Verse:
I've got joy like a fountain...

Third Verse:
I've got love like an ocean...

And here is "Scotland's Burning." Of course, Mocha doesn't play it as a round:

NEW
70 N=1
80 FOR X=1 TO 24
90 READ A,T
100 SOUND 261-N*A,T
110 NEXT X
120 DATA 12,4,12,4,9,4,9,4
130 DATA 12,4,12,4,9,4,9,4
140 DATA 8,8,7,8,8,8,7,8
150 DATA 6,8,6,8,6,8,6,8
160 DATA 12,4,12,4,9,4,9,4
170 DATA 12,4,12,4,9,4,9,4

Lyrics:
Scotland's burning,
Scotland's burning!
Look out!
Look out!
Fire! Fire!
Fire! Fire!
Pour on water,
Pour on water.

Once again, these songs play in the key of white D major pentatonic. The closest we can get to the key of A is to change line 70 to N=11 (key of lu A below white A) or N=21 (key of red A).

New Xenharmonic Wiki

Last year, I wrote that the Xenharmonic Wiki would no longer exist. Well, as it turns out, the Xenharmonic Wiki is back:

https://en.xen.wiki/

Even though I've linked to this site in the past, recall that most of the links at this site are EDO's, or equal divisions of the octave. But Mocha music is based on EDL's, or equal divisions of length. But there are a few pages on this wiki that are relevant to Mocha music.

First of all, it's possible to approximate some of the EDO's in Mocha EDL. This is mainly true for the macrotonal EDO's -- the ones where each step is larger than the usual standard (12EDO) steps. Here are the best approximations to the macrotonal EDO's in Mocha EDL:

7EDO: Degrees 156, 141, 128, 116, 105, 95, 86, 78
8EDO: Degrees 202, 185, 170, 156, 143, 131, 120, 110, 101
9EDO: Degrees 132, 122, 113, 105, 97, 90, 83, 77, 71, 66
10EDO: Degrees 256, 239, 223, 208, 194, 181, 169, 158, 147, 137, 128
11EDO: Degrees 162, 152, 143, 134, 126, 118, 111, 104, 98, 92, 86, 81

Subtract 261 from each of these Degrees to obtain the corresponding Sounds.

Extending this to the microtonal EDO's -- the ones where each step is smaller than the usual 12EDO steps -- is less accurate and is not generally recommended. But then again, last year I wrote an Easter song in 28EDO and played it on Mocha. To understand why I did so, you must know what I was thinking when I created that song.

I was fascinated by the fact that the Easter date, while seemingly random, followed patterns. For example, the next three Easters fall on April 21st, 12th, 4th. The first two dates are nine days apart and the last two are eight days apart. There are other sequences of three consecutive years that follow this same pattern:

1995-1996-1997: April 16th, April 7th, March 30th
2063-2064-2065: April 15th, April 6th, March 29th

I was hoping to take advantage of these patterns to make a tune based on the Easter dates -- for example, nine days could be a major third and eight days a minor third. Then all three of these patterns correspond to triads -- either major or minor, depending on how I decided to convert dates into notes.

At the time, I'd never heard of alternate scales (other than 12EDO, of course). But a simple correspondence didn't work out.

Then when I read a book written by Theoni Pappas, I learned about EDO scales. I was researching these scales and realized that 28EDO best preserves the patterns found in the Easter dates.

It was afterward when I discovered the Mocha emulator of my old computer. I remembered the Sound command and was curious about how the computer could play microtonal music. After a few tries, I learned that Mocha used EDL's, not EDO's. Still, it was the only way I knew to play music in anything other than 12EDO, and so I composed the 28EDO Easter song in it. It's not quite as accurate as a real 28EDO instrument, of course.

Since I wrote my 28EDO song in Mocha EDL, I suppose it's reasonable to estimate all microtonal scales between 12EDO and 28EDO in Mocha. But no higher EDO beyond 28EDO is recommended.

As a microtonal scale, 28EDO isn't one of the more common scales. It is notable for having a very accurate 5/4 major third at the ninth step of 28EDO. (Thus all those nine-day intervals between Easters map to major thirds.) But unfortunately, 28EDO lacks an accurate 3/2 perfect fifth. As we saw when trying to convert the guitar songs into EDL's above, I keep using 18EDL (with a just perfect fifth on the root note) over 20EDL (with a just major third over the root instead). This is especially true because the usual 12EDO scale has such an accurate perfect fifth, so our ears demand more accurate fifths compared to accurate thirds.

Is it possible to write the Easter song in an EDL scale instead of an EDO? For example, what if we were to map March 22nd-31st to Degrees 22-31 and April 1st-25th to Degrees 32-56? The resulting song would be considered 56EDL. Notice that 56EDL and 28EDO have the same number of steps in an octave, namely 28.

But unfortunately, EDL's hide the patterns we find in the Easter dates. For example, let's revisit the pattern I mentioned above:

1995-1996-1997: April 16th, April 7th, March 30th
2019-2020-2021: April 21st, April 12th, April 4th

Converting these to 56EDL, the first triad is 47:38:30 while the second is 52:43:35. These are not the same triad. For example, 47/38 is about 368 cents while 52/43 is about 329 cents. Neither one of these is equivalent to the major third of 28EDO (386 cents) -- and indeed, both of these would be the same triad in 28EDO while they are distinctly sounding triads in 56EDL.

Then again, EDL scales contain just major thirds, even more accurate than 28EDO. We might at least wish to modify the Mocha approximation of 28EDO (which, as I wrote above, isn't accurate) to include as many just 5/4 intervals as possible.

Here is Mocha's best approximation of 28EDO:

28EDO: Degrees 210, 205, 200, 195, 190, 186, 181, 177, 172, 168, 164, 160, 156, 152, 148, 145, 141, 138, 134, 131, 128, 125, 122, 119, 116, 113, 110, 108, 105

And here is our modified version:

28EDO: Degrees 210, 205, 200, 195, 190, 185, 180, 176, 172, 168, 164, 160, 156, 152, 148, 144, 141, 138, 135, 132, 129, 126, 123, 120, 117, 114, 111, 108, 105

Here we start with multiples of five from Degree 210 to 180 and then switch to multiples of four from Degree 180 to 144. This allows several 5/4 major thirds to appear: 210/168, 205/164, 200/160, 195/156, 190/152, 185/148, and 180/144 are all just major thirds. After 144 I switched to multiples of three instead. This results in several 4/3 perfect fourths appearing as well: 180/135, 176/132, 172/129, 168/126, 164/123, 160/120, 156/117, 152/114, 148/111, and 144/108 are all just fourths. In fact, this is an improvement over pure 28EDO, which lacks just fourths (and fifths).

The modified version of 28EDO can be coded in Mocha. We either use three For loops -- one loop each for five-, four-, and three-degree steps -- or include the whole list in Data lines.

Here is the link to 28EDO on the new Xenharmonic Wiki:

https://en.xen.wiki/w/28edo

And before we leave the Xenharmonic website, let me link to Kite's color notation, which I still use to describe EDL scales as well:

https://en.xen.wiki/w/Color_notation

This link includes the new version of Kite's color notation (including the use of "azure" or "zo" to mean "blue," and "lavender" to mean 11-limit).

Notice that Mocha EDL's are utonal. This means that only the colors that contain "u" in their symbols (plus white) are needed for Mocha:

Limit  Color
3         white (wa)
5         green (gu)
7         red (ru)
11       lavender (lu)
13       thu

Coding Kite Colors in Mocha

It's possible to write a simple program in Mocha where we enter a Sound from 1-255. The program converts this to a Degree (by subtracting it from 261) and then naming it using Kite colors.

NEW
10 INPUT "SOUND";S
20 D=261-S
30 C$=" ":L=2:K=3
40 P=2:S$="":GOSUB 200
50 P=3:S$="":GOSUB 200
60 P=5:S$="GU":GOSUB 200
70 P=7:S$="RU":GOSUB 200
80 P=11:S$="LU":GOSUB 200
90 P=13:S$="THU":GOSUB 200
100 IF D>1 THEN P=D:S$=STR$(P)+"U":GOSUB 200
110 IF C$=" " THEN C$="WA"+C$
120 A=INT(L*12/7+.4)-K
130 L=L-INT(L/7)*7
140 N$=CHR$(71-L)
150 IF A>0 THEN N$=N$+STRING$(A,"#")
160 IF A<0 THEN N$=N$+STRING$(-A,"-")
170 PRINT C$+N$
180 SOUND S,16
190 END
200 Q=D/P
210 IF Q>INT(Q) THEN RETURN
220 D=Q
230 C$=S$+C$
240 L=L+INT(LOG(P)/LOG(2)*7+.5)
250 K=K+INT(LOG(P)/LOG(2)*12+.5)
260 GOTO 200

Here's how the program works. After the Sound is converted to a Degree (D), Mocha starts finding the factors of D. Here C$ (the color) starts out as blank space (Line 30), and if it remains as a blank space (Line 110) then the color must be "white" (the syllable "wa"). Lines 40-90 contain syllables for the primes 2 through 13, including a null string "" for primes 2 and 3.

Line 100 assumes that any factor left after sieving out primes 2 through 13 must be prime (since the smallest possible composite would be 17^2 = 289, but the highest Degree in Mocha is 260). The syllable for these primes is the prime followed by "u" (17u, 19u, 23u, and so on).

The subroutine starts at Line 200. Here we keep track of both the letter name in L and the keyspan (which determines sharp of flat) in K. The flats are printed as "-" in Mocha because this is what the Play command also uses for flats.

Lines 240 and 250 use a 12EDO framework to determine the name of the note. Here Degree 11 ends up as Bb and Degree 13 becomes G#. Even Kite himself admits that the names for 11 or 13 can go either way (lu B or lu Bb for 11, thu G or thu G# for 13). I myself tend to use B and G for 11 and 13, but the 12EDO framework requires Bb and G# (since 11/8 is closer to an augmented 4th than a perfect 4th, and 13/8 to a minor 6th than a major 6th in 12EDO). Kite would write "ilo 4th=P4, tho 6th=M6) for my method and "ilo 4th=A4, tho 6th=m6" for Mocha's.

After returning from the subroutine, L and K are used to determine the note name. Here L=0 denotes the note G, L=1 is F, and L=2 is E, and so on. (The note names are backwards because EDL's are utonal/undertones.) And K=0 is also G, but K=1 is F#, K=2 is F, K=3 is E, and so on. (Line 30 starts at N=2, K=3 because the fundamental corresponding to Degree 1 is E.) Line 120 uses .4 for the rounding instead of .5 only because .5 happens to place a 12EDO note between B and C instead of between A and B as is proper for (American) 12EDO. (Germans like Bach actually would put an extra note between B and C, called H! But we don't want Mocha to follow the German convention.)

Line 170 prints the color and note name, Line 180 plays the Sound, and Line 190 ends the program.

Here are the names determined by Mocha for all the Sounds in the 200's (Degrees 6-61):

Sound  Degree  Note
255       6           wa A
254       7           ru F#
253       8           wa E
252       9           wa D
251       10         gu C
250       11         lu Bb
249       12         wa A
248       13         thu G#
247       14         ru F#
246       15         gu F
245       16         wa E
244       17         17u D#
243       18         wa D
242       19         19u C#
241       20         gu C
240       21         ru B
239       22         lu Bb
238       23         23u A#
237       24         wa A
236       25         gugu Ab
235       26         thu G#
234       27         wa G
233       28         ru F#
232       29         29u F#
231       30         gu F
230       31         31u E#
229       32         wa E
228       33         lu Eb
227       34         17u D#
226       35         rugu D
225       36         wa D
224       37         37u Db
223       38         19u C#
222       39         thu C#
221       40         gu C
220       41         41u B#
219       42         ru B
218       43         43u B
217       44         lu Bb
216       45         gu Bb
215       46         23u A#
214       47         47u A
213       48         wa A
212       49         ruru G#
211       50         gugu Ab
210       51         17u G#
209       52         thu G#
208       53         53u G
207       54         wa G
206       55         lugu Gb
205       56         ru F#
204       57         19u F#
203       58         29u F#
202       59         59u F#
201       60         gu F
200       61         61u E#

Notice that I use the syllables ("gu," "ru") rather than the full colors ("green," "red"). This is so that Mocha can combine the syllables if needed ("gugu," "rugu"). I could have used "white" in Line 110 since this is never combined with another color, but I used "wa" for consistency.



Operation Varsity Blues

I did say earlier that I'd write about the recent college admissions scandal. Yes, on the anniversary of the day I got into UCLA, I'm discussing how others got into UCLA, USC, and other schools. As it turns out, this scandal has a name, "Operation Varsity Blues." It's named for a movie that came out 20 years ago -- just two and half months before I received my UCLA admissions letter.

Operation Varsity Blues is causing everyone to rethink about what students need to do to gain admissions to selective college. We all agree that students who pretend to play sports that they don't actually play is an illegitimate way to get into selective colleges.

But some people are starting to wonder whether colleges admissions offices are too reliant on SAT, ACT, and AP exams. Just this month, I've written extensively about how my new district, unlike many others, offer AP English Language to sophomores and AP English Literature to juniors.

Again, I wonder whether these early AP's are intended to help students get into colleges. After all, the AP's I personally took in my senior year didn't help me get into UCLA, since I didn't get the scores of those AP's until about four or five months after I received my fat envelope from UCLA. The only AP scores that helped me get into UCLA are the ones I took as a junior -- and in general, only AP's taken no later than 11th grade are seen by admission decision makers. By taking the AP exams a year early, this allows an extra score to be seen by decision makers before fat envelopes are sent out.

So far, I haven't seen as much for early AP math classes -- but then again, AP Calculus is much more difficult than AP English Lit. I did write earlier about the two seventh graders in Algebra I -- those two students might be headed for junior year Calculus.

I often consider the tweeter CCSSIMath to be a traditionalist. This user has retweeted several articles this month pertaining to the Operation Varsity Blues scandal:

https://twitter.com/CCSSIMath

But unlike the other traditionalists, CCSSIMath doesn't agree completely with the push to place everyone in Algebra I in seventh or eighth grade. The user links to the following article:

https://www.chicagotribune.com/suburbs/deerfield/news/ct-dfr-district-109-math-curriculum-concerns-tl-0321-story.html

Some said they’re starting to see negative results with the district’s decision to cut the “regular” math course for seventh graders this year, leaving them with the options of taking an accelerated or advanced class.

Here the accelerated class leads to completing Algebra I in eighth grade, while the advanced class is itself seventh grade Algebra I. What I'm wondering is, is the reason to dropping regular Common Core Math 7 related to making students more competitive for college.

I'm not quite sure whether there is a simple solution to this problem. I recall reading about how college admissions are different from most other businesses. For example, successful eateries such as McDonalds used to brag about how many customers they had -- "99 billion served." But Ivy League colleges do the opposite -- they brag about how few students get into their schools, not how many.

But the only way to make colleges more like fast food is if the most successful colleges -- say the Ivy League trio of Harvard, Princeton, and Yale -- educated the most people. Imagine if almost every college -- even community colleges -- were run by Harvard, Princeton, and Yale. Then many more people could earn diplomas from those schools, and so Operation Varsity Blues would disappear.

Of course, I can't see how that could work in reality. So far, I don't know a solution to the college admissions scandal.

Bruce William Smith

It's been a while since the traditionalist Bruce William Smith has posted. He used to be active at Edsource, but not lately. Recall that Smith's zeal for earlier advanced math goes one step further even than SteveH. SteveH promotes eighth grade Algebra I and senior year Calculus, but Smith prefers seventh grade Algebra I and junior year Calculus!

Yes, this means that the schools in Deerfield, Illinois (CCSSIMath link above) are placing all students into either accelerated (SteveH-level) or advanced (Smith-level) classes. And I subbed in two eighth grade Algebra I classes (SteveH-level), and in each class there was one seventh grader (Smith-level).

Anyway, Smith has now been posting at the Joanne Jacobs site -- a site I often go to in order to find certain other traditionalists. So let's find out what he's been up to:

https://www.joannejacobs.com/2019/03/why-kids-need-to-learn-standard-english/

This post is a who's who among traditionalists. Not only does Smith make his first comment in response to this post, but also among the commenters are Bill (a regular at the Jacobs site) and Ze'ev Wurman (who occasionally comments here). Moreover, Jacobs even links to a blog (co-)authored by another traditionalist I haven't seen in some time -- Katharine Beals!

But the post that has drawn so many traditionalists has nothing to do with math. The topic of this post is English -- standard English, to be exact. And unfortunately, this post is racial, since it's all about black students and whether they should speak Standard American English or the dialect known as African-American Vernacular English.

So far, I've seen Smith mainly write about math in his traditionalism comments. But Bill, Wurman, and Beals have all discussed traditional English instruction as well. On the other hand, we already know that race (specifically tracking) is a fairly common talking point among traditionalists.

Since this is a racial discussion, that's why I had to delay writing about this grand traditionalists' reunion until spring break. I try to bury controversial racial discussions at the bottom of vacation posts (though this was impossible when reading Eugenia Cheng's latest book).

Let's start with the original Jacobs post, which as usual contains a link of its own:

Black kids need to learn Standard American English (SAE), writes Jasmine Lane, an English teacher in training, in her excellent blog.
It was called “talking white” when she was growing up as “a poor, Black girl from the north side of Minneapolis with two working-class parents and one who didn’t finish the 9th grade.”

Now here are our traditionalists. Let's start with Smith, whose return first drew me to this post:

brucewilliamsmith:
Standardization in English (and other languages) is more applicable to its written than its spoken form; AAVE is distinguished from standard English in its grammar as well as its vocabulary, to a point, in extreme versions (such as Gullah), where it may be argued to be a separate dialect rather than a mere variety of English.

Next up is Bill:

Bill:
Does anyone remember ebonics, which was derided even by Jesse Jackson when it proposed many years ago in the Oakland school district (at least I think it was Oakland)…
As I recall it wasn’t around for very long

As a Californian, I'll inform readers that yes, it was indeed Oakland. The third traditionalist to comment is Wurman:

Wurman:
I would agree too, not only Henry Higgins. ðŸ™‚
I welcome the dose of common sense she represents.

Here "Henry Higgins" is a character from the My Fair Lady clip that Jacobs includes in her post. I assume that "she" refers to Lane, the author of the blog at the first link.

I won't quote Katharine (or Catherine) here on this blog, but it's significant to note that the post at the link is all about diagramming sentences -- something that traditionalists (of English class) wish that students still do nowadays.

Yesterday I subbed in a music class. The students were singing spiritual songs to prepare for their trip to Carnegie Hall. Many spirituals have their roots in the black church, and so some of their lyrics are written in AAVE. I heard the sopranos (none of whom are black, by the way) sing about going to the "promis' lan'," and I believe the word "nevah" appeared in the song as well.

So let me conclude the racial portion of this post with my own opinion on this issue. We might wonder why black students speak AAVE and have trouble learning Standard English. Well, the answer is that from ages 0-5, all the young black students hear nothing but AAVE from the parents, and old habits are hard to break once they reach school age. So now we wonder do the parents speak AAVE and have trouble learning Standard English. Well, the answer is that from ages 0-5, all the parents heard nothing but AAVE from the grandparents, and old habits are hard to break once they reach school age. So now we wonder do the grandparents speak AAVE and have trouble learning Standard English. Well, the answer is that from ages 0-5, all the parents heard nothing but AAVE from the great-grandparents...and so on.

And after we go back sufficiently many generations, we reach one where during ages 0-5, the language they spoke wasn't any English dialect, but an African language that they were speaking on the continent of Africa. This language probably wouldn't have been Swahili (which I mentioned earlier in this post). For example, Kunta Kinte in Alex Haley's Roots spoke Mandinka. As the Africans began to learn English, their speech was influenced by their native languages, and hence AAVE was born.

Thus in order to break the AAVE cycle, we'd need a generation that hears nothing but Standard English for the first sixty months of their lives. Then this generation can grow up and teach Standard English to their children. But once again, I don't know how achievable this is.

Jasmine Lane (the author of the link above) tells us that black students must make a choice between their native dialect that they naturally want to speak (AAVE) and the dialect that leads to success in the real world (Standard English). On the other hand, whites don't have to make such a choice, since their native dialect is the same as the dialect that leads to success. This is the source of the debate -- blacks must make a choice that whites don't have to make.

Unlike Lane, I am not an English teacher, and so much of the AAVE debate isn't relevant to me. But there is one part of AAVE that is relevant to me as a math teacher -- student names.

It's well-documented that certain names are the equivalent to AAVE -- they are strongly associated with being black. And ceteris paribus, job candidates with resumes containing the AAVE names are less likely to be called for interviews than those containing SAE names. (Notice that some of these names actually are Swahili, such as Imani -- named for the last principle of Kwanzaa and is equivalent to the name Faith in SAE.) And no matter how much black students change their dialect from AAVE to SAE, they can't as easily change their name.

When I was at the old charter school two years ago, recall that almost all of the eighth graders there were black. At the start of the year, one girl was clearly at the top of her class. I won't reveal her name here, but I will say that her name contains an apostrophe. Names with apostrophes (unless they are Irish names beginning with "O'-") are strongly associated with being black. (This is the "neutral girl" from my January 6th post.)

And even this week, I notice that one of the two seventh graders in the Algebra I class was black. He has a common Biblical name, except that one of the letters is replaced with a "z."

These two students are clearly strong math students and might even apply for high-paying STEM jobs in the future. But I fear that the apostrophe or "z" in their names might lead to their resumes being rejected.

At the old charter school, I was considering telling the girl that when she sends a resume to a company someday, she should spell her name without an apostrophe. (Save the apostrophe for after she's hired and she's filling out her W-4 forms.) But she moved away from the school after a month and I never got to say this to her.

And of course I didn't give this sort of advice to the Algebra I seventh grader, since I only knew him for two days. (He was also in one of the science classes I subbed for later in the week.) Indeed, this is the sort of thing I'd only tell a student at the end of the year, after the student has attended my class for an entire year and learned to trust me.

Conclusion

Notice that race isn't the only controversial topic I wrote about in this spring break post. Somehow, religion has quietly dominated the two spring break posts, from calculation of the date of the religious holiday Easter to the lyrics of spiritual songs to students with Biblical names.

Just as I ordinarily don't post "A Day in the Life" when one of my districts is on spring break, I normally wouldn't post a worksheet from such a day. But I can't help but post the following worksheet today because it fits my most recent U of Chicago lesson like a glove.

On the day I subbed for Algebra I, the teacher assigned an extra credit worksheet. One side of the worksheet was a Pizzazz worksheet on simplifying radicals. But the other side just happened to be a logic problem about college roommates.

Of course I have to post the logic problem today, since it fits perfectly with Lesson 13-6 and the logic problem I posted last week. And it's all about college roommates, which also goes well with today's UCLA anniversary post.

As for our next lesson, spring break ends and I'll cover Lesson 13-7 in my next post, scheduled for Monday, April 1st. For those who have completed spring break, I hope you enjoyed it. For those who are just starting spring break, I hope you'll have fun. And those of you for whom spring break is still a week or more away, just sing the Big March song and hopefully you'll get through this tough time.

Sunday, March 24, 2019

Why Isn't Today Easter?

Table of Contents

1. Happy Easter!
2. Orthodox and Gregorian Easter
3. Aleppo Easter Proposal
4. Early Easters
5. Late Easters
6. The Exceptional Years 1981, 2000, 2019
7. Calendar Reform and Easter
8. The Lunisolar Dee Calendar
9. Easter on David's Lunar Calendar
10. Conclusion

Happy Easter!

That's right -- today is Easter Sunday. And I'll prove it to you. Let's start with a definition of Easter, courtesy the Oxford Dictionary:

https://en.oxforddictionaries.com/definition/easter

The most important and oldest festival of the Christian Church, celebrating the resurrection of Christ and held (in the Western Church) between 21 March and 25 April, on the first Sunday after the first full moon following the northern spring equinox.

And so let's check out the calendar. According to the calendar on the wall, the spring equinox was on March 20th, and the first full moon following that equinox was on March 21st. Thus Easter must be on the first Sunday following the March 21st full moon -- and that's today, March 24th. Therefore today is Easter. QED

Of course, you know that this proof must be flawed, because you put your Easter basket out and it's still empty, so the Easter Bunny hasn't come yet. So where is the flaw in my proof?

Well, you might check your own calendar and see that the full moon was on March 20th, while my calendar gives it as the 21st. The difference is caused by time zones. My calendar is based on Greenwich Mean Time, while yours, like many American calendars, is based on Eastern Time. On your calendar, the equinox and the full moon both occurred on March 20th.

But then again, nowhere in the above definition does it preclude the equinox and full moon falling on the same day. As long as the full moon follows the equinox -- even if it's just by a minute, even if it's just by a second -- then the following Sunday should be Easter.

And it's obvious that the full moon occurred after the equinox, since there exists a time zone (namely Greenwich) in which the equinox occurred on the 20th and the full moon on the 21st. But just to be sure, let's check the times of the equinox and full moon in a single time zone -- I'll choose my own time zone, Pacific Time:

Spring Equinox: March 20th at 2:58 PM
Full Moon: March 20th at 6:43 PM

Thus the full moon occurred 3 3/4 hours after the equinox. Since the full moon follows the equinox, that proves that the following Sunday, today is Easter.

So why isn't today Easter?

Orthodox and Gregorian Easter

In the Oxford definition of Easter, we notice the phrase "in the Western Church." This implies that in some churches that aren't Western, Easter might fall on a different day. And indeed this is true -- the Orthodox churches observe Easter on a different day.

So is today Orthodox Easter? No, it isn't. In fact, this year Orthodox Easter is even later than the Western Easter that you're used to. Western Easter is on April 21st, while Orthodox Easter is a week later, on April 28th. Indeed, Western Easter Sunday is Orthodox Palm Sunday.

But why is Orthodox Easter later than Western Easter? At first, it's apparent that it has something to do with the old style Julian vs. the new style Gregorian Calendar. In my last few posts, we celebrated the composer J.S. Bach with his Google Doodle. Ordinarily, Google Doodles appear on birthdays, so was it Bach's birthday?

It depends on the calendar. Bach grew up celebrating his birthday on March 21st, 1685. But he was born in Protestant Germany. A century earlier, Pope Gregory had announced the calendar named for him, the Gregorian Calendar, but at first only Catholic countries followed the new calendar. Most Protestant countries were slow to accept the change, and the Orthodox even slower.

Pope Gregory formed his calendar by dropping ten days from the Julian Calendar. Therefore Julian March 21st, Bach's birthday, was Gregorian March 31st. Notice that Google posted the doodle on Gregorian March 21st, which isn't his birthday. But once again, it's the day that Bach himself considered to be his birthday. By the time Bach died, Germany had accepted the Gregorian Calendar, and so his death day was Gregorian July 28th.

(The same thing happened with George Washington. He was born in the Protestant British colonies on Julian February 11th, and he died on Gregorian December 14th. But the holiday that eventually became known as Washington's Birthday was February 22nd, his Gregorian birthday.)

OK, so there are two calendars, the Julian and Gregorian. But in theory, the existence of two calendars shouldn't affect the day of Easter. After all, the equinox is the equinox and the full moon is the full moon. These are astronomical events that occur no matter what day the calendar says it is. So unless the two calendars disagree on whether today is Sunday (and they don't), then today should be Easter on either calendar.

But the fact that there are two different Easters at all -- April 21st and 28th -- implies that there must be more to the Easter date than just the equinox and full moon. Thus in order to answer the question:

Why isn't today Easter?

the following question might give us a hint:

Why are Gregorian Easter and Orthodox Easter on different dates?

Let's start with a history of the computus -- the calculation of the Easter date:

http://php.net/manual/en/function.easter-days.php

The date of Easter Day was defined by the Council of Nicaea in AD325 as the Sunday after the first full moon which falls on or after the Spring Equinox. The Equinox is assumed to always fall on 21st March, so the calculation reduces to determining the date of the full moon and the date of the following Sunday. The algorithm used here was introduced around the year 532 by Dionysius Exiguus. Under the Julian Calendar (for years before 1753) a simple 19-year cycle is used to track the phases of the Moon.

And we've seen that 19-year cycle before -- it's the Metonic Cycle.

But this paragraph explains where the Easter date comes from. In the year 532, a Christian monk named Dionysius Exiguus created a table of 19 different full moon dates -- a table that repeats every nineteen years. So when it was time to determine Easter, no one looked at the sky to see whether the moon was full or not. Instead, they just looked at the chart to see when the full moon was -- a date known as the Paschal full moon. Then the following Sunday was Easter.

In other words, the Easter rule was rule-based, not observation-based. Originally, the Chinese Calendar was also rule-based, but now it's based on astronomical observations. And the Julian Calendar, is also rule-based.

As for the Gregorian Calendar, the above link explains:

Under the Gregorian Calendar (for years after 1753 - devised by Clavius and Lilius, and introduced by Pope Gregory XIII in October 1582, and into Britain and its then colonies in September 1752) two correction factors are added to make the cycle more accurate.

In other words, the Gregorian Calendar is also rule-based. Actually, there is one small part of the Gregorian Calendar that is observation-based -- the insertion of leap seconds. Everything else, including the calculation of Easter, is based on rules.

The link states that there are two correction factors. Easter is, after all, a holiday determined by both the sun and the moon. One of the correction factors is solar while the other is lunar.

The solar correction is well-known -- certain years have Leap Days in the Julian Calendar but not in the Gregorian Calendar, such as 1900 and 2100. The lunar correction is less familiar. It's related to the fact that the Metonic Cycle isn't perfectly accurate. I wrote about how to improve upon the Metonic Cycle back in my December 28th post on calendars.

But we see the lunar correction at work when we compare Gregorian and Orthodox Easter. The next full moon, according to my calendar, is April 19th, and Easter is the next Sunday, April 21st. But Orthodox Easter is based on the old Dionysius Exiguus tables, which are inaccurate since the erros in the Metonic Cycle are noticeable after 1500 years. By now, the tables are three or four days late, so instead of April 19th, the Orthodox Paschal Full Moon is on April 22nd or 23rd. Thus Orthodox Easter isn't until the following Sunday, April 28th.

It's the solar correction, however, that I wish to focus on now. As I quoted above, the equinox is always considered to fall on March 21st in the respective calendar -- Julian or Gregorian. And as I wrote earlier, in Bach's day the Julian "equinox" didn't occur until Gregorian March 31st. This means that the Paschal full moon, and thus Easter, could never fall earlier than that equinox. From that point on, if a Gregorian Easter fell in March, then the Orthodox Easter wouldn't fall until the next full moon, an entire month later.

In the Gregorian Calendar, the equinox is considered to fall on our March 21st. But as we see on our calendars, the actual equinox this year was on the 20th, not the 21st. The Gregorian Calendar is far more accurate than the Julian Calendar, but no rule-based calendar is perfect. Oh, you might be wondering about the fact that the full moon really was on the 21st in some time zones. Well, the Paschal full moon is calculated from tables -- and tables don't know anything about time zones.

And so this is why today isn't Easter. It would be Easter if we were using an observation-based calendar, but our actual calendar is rule-based. And based on the rules devised over 400 years ago, the full moon fell before the equinox, so Easter isn't until the after next full moon, a month from now.

Aleppo Easter Proposal

About 20 years ago, there was a proposal to define Easter based on astronomical events. This is mentioned at the bottom of the following link:

http://www.webexhibits.org/calendars/calendar-christian-easter.html

At at meeting in Aleppo, Syria (5-10 March 1997), organised by the World Council of Churches and the Middle East Council of Churches, representatives of several churches and Christian world communions suggested that the discrepancies between Easter calculations in the Western and the Eastern churches could be resolved by adopting astronomically accurate calculations of the vernal equinox and the full moon, instead of using the algorithm presented above. The meridian of Jerusalem should be used for the astronomical calculations.

And that's the only logical time zone where the calculation should take place -- after all, Easter commemorates the crucifixion of Jesus Christ, and that event took place in Jerusalem. Thus it makes sense to choose the Jerusalem time zone to determine when it is Sunday.

By the way, Jerusalem is two hours ahead of Greenwich. Daylight Saving Time is observed two days earlier than in Greenwich -- the Friday before the last Sunday in March. (I believe that the clocks move forward on Friday rather than Sunday so that they're set forward before the Jewish Sabbath starts the following sunset.)

Aleppo Easter was supposed to be implemented starting in 2001. It would replace both Gregorian and Orthodox Easter, thus allowing all Christians to celebrate Easter the same day. Notice that according to the link, 2019 would indeed be the first year when Aleppo Easter differs from Gregorian Easter:

If the new system were introduced, churches using the Gregorian calendar will hardly notice the change. Only once during the period 2001-2025 would these churches note a difference: In 2019 the Gregorian method gives an Easter date of 21 April, but the proposed new method gives 24 March.

And yes -- we already determined at the start of this post that today is Aleppo Easter. So obviously, this means that the Aleppo Easter proposal was never adopted, since no one celebrates Easter today.

And before you ask, yes, it is spring break in my old district, but no, it's not because our district secretly decided to observe Aleppo Easter. In our district, spring break has nothing to do with Easter at all. If today had been Easter, then there would have been no school two days ago, since it would have been Good Friday. (Good Friday and Easter Monday are always holidays in my old district.)

Notice that an April 21st Easter is preferable to March 24th for people living in cold northern climates where there is still snow on the ground as late as early-to-mid April. On the other hand, perhaps those in Australia and New Zealand wish that today were Easter after all.

But what about teachers and students in schools? Those attending schools with Easter break might be longing for the holiday to come (during the "Big March"). Then again, they'd return to school after Easter and find that there are no more holidays for two months, until Memorial Day.

In my old school district, late Easters may be desirable because this week is spring break no matter when Easter is. Thus we get both spring break and a four-day Easter weekend, whereas if today were Easter, we'd get only spring break.

On the other hand, schools in Boston observe spring break the week of Patriots' Day -- the third Monday in April. They also close on Good Friday. But if this is the Friday after Patriots' Day (as it is in 2019), then there is no extra holiday. Thus Boston students and teachers might wish that today were Easter, so that they'd get separate holidays for both Good Friday and spring break, instead of just spring break.

On the other hand, Bostonian adults who don't work at schools might prefer the late Easter in order to avoid cold New England weather. Thus what students and teachers want is often at odds with what non-school adults prefer. I notice that in Boston, today the high is near 60 degrees with temps closer to freezing with snow chances both before and after -- if only today were Easter. (Go figure!)

There's one more interesting thing mentioned at the above link:

Note that the new method makes an Easter date of 21 March possible. This date was not possible under the Julian or Gregorian algorithms. (Under the new method, Easter will fall on 21 March in the year 2877. You’re all invited to my house on that date!)

Under either Gregorian or Julian Easter, the range of possible Easter dates is March 22nd-April 25th in the respective calendar. (Julian March 22nd-April 25th currently corresponds to April 4th-May 8th on the Gregorian Calendar.) The link tells us that Aleppo Easter will fall on March 21st, 2877 -- and who knows, maybe the Aleppo Easter proposal will finally be adopted by the 29th century.

But wait a minute -- Aleppo Easter is determined by observation, not a rule or formula. So how can we know when the full moon will be over 800 years from now?

Actually, astronomical full moons can be calculated -- it's just that the calculations are much more sophisticated than those used by Exiguus or Lilius/Pope Gregory. (Indeed, we've seen that solar and lunar eclipses can be calculated up to a millennium in advance.) In this case, 2877 will be just like 2019, with an equinox followed by a full moon on March 20th. The difference is that March 20th, 2877 is a Saturday, allowing Easter to fall on Sunday, March 21st, 2877.

This is a math blog. It's possible that some of you readers are new -- you stumbled upon this post by searching for Google when you realized that today was supposed to be Easter, but isn't. Well, your question has been answered. The rest of this post includes some complex math calculations related to Easter, full moons, and equinoxes. Unless you're a math teacher or mathematically inclined, I recommend that you stop reading this post and check out other Google results. For example, I found the following Farmer's Almanac link:

https://www.farmersalmanac.com/when-easter-10797

Early Easters

Obviously, March 21st, 2877 would be an especially early Easter. The earliest Easter can fall on the Gregorian Calendar is March 22nd. This date is particularly rare. According to the following link:

http://tlarsen2.tripod.com/thomaslarsen/easterdates.html

the last time Easter fell on March 22nd was 1818, and the next time won't be until 2285. Why is the earliest possible Easter so rare?

Last year, Easter fell on April 1st -- which isn't nearly as rare. Knowing that Easter date, let's go backwards and determine the date of the Paschal Full Moon. There are seven possibilities:

Sunday, March 25th
Monday, March 26th
Tuesday, March 27th
Wednesday, March 28th
Thursday, March 29th
Friday, March 30th
Saturday, March 31st

As it turns out, the last date above was the Paschal Full Moon for 2018. Now let's work backwards to determine the Paschal Full Moon for a March 22nd Easter:

Sunday, March 15th
Monday, March 16th
Tuesday, March 17th
Wednesday, March 18th
Thursday, March 19th
Friday, March 20th
Saturday, March 21st

But we know that since the equinox was defined as March 21st, the Paschal Full Moon can't occur on March 20th or earlier. So the list of possible Paschal Full Moons becomes:

Saturday, March 21st

There's only one possible Paschal Full Moon for a March 22nd Easter, while there are in fact seven possibilities for an April 1st Easter. This is why April 1st Easters are about seven times as common as March 22nd Easters. In order to have a March 22nd Easter, not only must the Paschal Full Moon be March 21st, but that date must be a Saturday so that the 22nd can be Easter Sunday.

When Exiguus first constructed his table of Paschal Full Moons, there were 19 possible full moon dates, one for each year of the Metonic Cycle. Only one of those dates was March 21st -- and only about 1/7 of those years was that date a Saturday. Thus the probability of a March 22nd Easter works out to be 1/19 * 1/7 = 1/133 -- that is, Easter on March 22nd occurs once every 133 years.

But the two years with Easter on March 22nd -- 1818 and 2285 -- are more than 400 years apart. Of course, these are Gregorian Easters that have nothing to do with the Exiguus tables.

How many possible Paschal Full Moon dates are there, anyway? It would seem that the first full moon of spring could fall at any time during the first month after March 21st -- that is, there are 30 possible full moon dates. But due to the Metonic Cycle, full moon dates repeat every 19 years. In other words, there are only 19 possible full moon dates, not 30. On the Exiguus tables, there are 19 full moon dates, not 30.

We know that the Gregorian tables have solar and lunar corrections. As it turns out, these corrections are applied only at years that are multiples of 100. (We already know that solar corrections occur in such years, and to make it simple, lunar corrections are applied in such years too.)

This means that within a given century, the 19 possible full moon dates are fixed, but different centuries can have different Paschal Full Moons. Within a given century, let's call a possible full moon date "golden" if it's one of the possible full moon dates in that century. I choose the name "golden" because it refers to the Golden Numbers used in the Easter calculation. The Golden Number of a year is one more than its remainder when divided by 19. So in a given century a "golden date" is the Paschal Full Moon corresponding to all the years in that century with the same Golden Number.

Let's also agree to call a possible moon date "silver" if it is not golden. If in a given century a certain date is silver, then it will not be the Paschal Full Moon date for any year in that century.

Notice that there can never be two silver dates in a row. If April 4th is silver, then both April 3rd and 5th must be golden. Likewise, there can never be three golden dates in a row. If April 2nd and 3rd are both golden, then both April 1st and 4th must be silver.

Now you can start to see what I'm getting at. The only possible Paschal Full Moon date for a March 22nd Easter is March 21st. But in centuries when March 21st is silver, the full moon can't fall on March 21st at all that centuries. Thus in such centuries, March 22nd can't be Easter. We'll have to wait until the next century -- or even several centuries -- until March 21st is golden again before March 22nd can be Easter.

Let's look at a table of Paschal Full Moons for the current 21st century:

Golden Number   Paschal Full Moon
1                           April 14th
2                           April 3rd
3                           March 23rd
4                           April 11th
5                           March 31st
6                           April 19th
7                           April 8th
8                           March 28th
9                           April 16th
10                         April 5th
11                         March 25th
12                         April 13th
13                         April 2nd
14                         March 22nd
15                         April 10th
16                         March 30th
17                         April 18th
18                         April 7th
19                         March 27th

The dates in this chart are the golden dates for the current century. The missing dates are all silver:

Silver Dates: March 21st, 24th, 26th, 29th, April 1st, 4th, 6th, 9th, 12th, 15th, 17th

And we observe that indeed, March 21st is silver this century, so March 22nd can't be Easter. It's also silver during the 20th and 22nd centuries, and so March 22nd isn't Easter in those centuries either. On the other hand, March 21st is golden during the 18th, 19th, and 23rd centuries. And indeed, all three centuries have a March 22nd Easter according to the above link (1761, 1818, 2285).

The earliest Easter in the 21st century is March 23rd. The possible Paschal Full Moons for a March 23rd Easter are:

Friday, March 21st
Saturday, March 22nd

Since there can't be two silver dates in a row, these can't both be silver. And in the current century, March 22nd is golden. Easter was early 11 years ago -- March 23rd, 2008.

Let's look for March 24th Easters, since today is March 24th and ought to be Easter. The possible Paschal Full Moons for a March 24th Easter are:

Thursday, March 21st
Friday, March 22nd
Saturday, March 23rd

Even though both March 22nd and 23rd are golden this century, it just so happens that neither is the Paschal Full Moon in a year when March 24th is on a Sunday. The last time today was Easter was back in 1940. The table at the above link doesn't even go far enough to the next March 24th Easter. It just so happens that Easter will fall on both March 22nd and 23rd before it falls on the 24th again.

As we go later in March, there are more possible full moon dates for each date of Easter. The possible Paschal Full Moons for a March 25th Easter are:

Wednesday, March 21st
Thursday, March 22nd
Friday, March 23rd
Saturday, March 24th

Of these, both March 22nd and 23rd are golden this century. Easter will fall on March 25th twice this century -- in 2035 and 2046.

By the way, there's one more thing to say about early Easters. It is impossible to Easter to fall in March in two years in a row. To see why, suppose Easter is on March 31st one year. This means that the latest possible Paschal Full Moon that year would be March 30th. But then there would be a full moon the following year on March 19th (11 days earlier, since 12 lunar months are 11 days shy of a solar year). But this is too early to be the Paschal Full Moon. Instead, the Paschal Full Moon would be a month later, leading to a late Easter in April.

In fact, not even an April 1st Easter can be followed by a March Easter in the Gregorian Calendar (even though this is exactly what happens with Aleppo Easter from 2018 to 2019). If Easter is on April Fool's Day, then the Paschal Full Moon is no late than March 31st. And once again, 11 days earlier is March 20th, which is too early for the Paschal Full Moon the following year.

Instead, the earliest Easter can be the year before a March Easter is April 2nd. This happens when the Paschal Full Moon is on April 1st. The following Paschal Full Moon is 11 days earlier on March 21st, with Easter the following Sunday -- most likely March 25th, possibly the 24th. This combination most recently occurred in 1893-1894 and will occur again in 2265-2266.

In centuries where March 21st is silver, April 3rd is the earliest Easter that can be followed by a March Easter. This most recently occurred in 1988-1989 and will occur again in 2140-2141.

Late Easters

When is the latest possible Easter? Consider the first Easter after I was born -- 1981. The Golden Number for this year is 6 -- and there was no solar or lunar adjustment in 2000, so the chart I listed earlier applies to both the 20th and 21st centuries.

So the Paschal Full Moon for 1981 was on April 19th. Since this was a Sunday, Easter would be a full week later -- April 26th. But let me tell you something -- April 26th, 1981 was not Easter on the Gregorian Calendar. Indeed, April 26th isn't even listed as a possible Easter date! So what gives?

On the original Exiguus charts, it just so happened that April 19th was silver. The latest possible golden date was April 18th, and so the latest possible Easter was a week later, April 25th. On the Orthodox Calendar, April 25th was the mirror image of March 22nd, since the list of Paschal Full Moon Dates for an April 25th Easter would be:

Sunday, April 18th

And both March 22nd and April 25th Easters would be equally rare.

But the Gregorian Calendar has solar and lunar adjustments. This opened up the possibility that April 19th, while silver in some centuries, might be golden in others. And in centuries when April 19th is golden, Easter could fall on April 26th. It turns out that the 20th century is such a century and that 1981 is such a year.

When the Gregorian Calendar was first devised, there was a slight tweak in the calculation of the Easter date, introduced for the sole purpose of preventing Easter from falling on April 26th. Here's the tweak -- if the calculation gives April 19th as the Paschal Full Moon, then just change April 19th to April 18th. So the Paschal Full Moon for Easter was April 18th, with Easter the next day, the 19th.

So if April 19th is golden, we change it to April 18th. In some centuries when April 19th is golden, it just so happens that April 18th is golden as well. It was decided that having two Golden Numbers share the same Paschal Full Moon in a century was undesirable. Thus in centuries when April 18th and 19th are both golden, not only do we change April 19th to the 18th, but we also change April 18th to the 17th.

Note that the second adjustment only occurs in centuries when both April 18th and 19th are golden. If April 18th is golden but the 19th is silver, then we don't adjust the golden April 18th. And since there can never be three golden dates in a row, the 17th, 18th, and 19th can't all be golden. Thus there's never a reason to adjust golden April 17th.

Let's extend our golden/silver analogy. Instead of referring to golden April 19th, we adjust it to April 18th and call it "fool's gold" or "pyrite." (If April 19th is silver, then April 18th remains golden rather than pyrite.) If both April 18th and 19th are golden, then we adjust these to the pyrite 17th and 18th.

So our current Paschal Full Moon table for the 20th and 21st centuries becomes:

Golden Number   Paschal Full Moon
1                           April 14th
2                           April 3rd
3                           March 23rd
4                           April 11th
5                           March 31st
6                           April 18th (pyrite)
7                           April 8th
8                           March 28th
9                           April 16th
10                         April 5th
11                         March 25th
12                         April 13th
13                         April 2nd
14                         March 22nd
15                         April 10th
16                         March 30th
17                         April 17th (pyrite)
18                         April 7th
19                         March 27th

Silver Dates: March 21st, 24th, 26th, 29th, April 1st, 4th, 6th, 9th, 12th, 15th

The pyrite dates break the symmetry between early and late Easters. March 22nd Easter is impossible in centuries when March 21st is silver, but April 25th is possible in all centuries because April 18th is always either golden or pyrite. Easter will next fall on April 25th in the year 2038.

Meanwhile, there is one year this century -- 2049 -- when Easter would have fallen on April 25th had it not been for the pyrite rule. Instead, the Paschal Full Moon for 2049 is pyrite April 17th and so Easter is on April 18th instead of the 25th.

In fact, the most common Easter date is April 19th. This is because not only are there seven possible Paschal Full Moons for an April 19th Easter:

Sunday, April 12th
Monday, April 13th
Tuesday, April 14th
Wednesday, April 15th
Thursday, April 16th
Friday, April 17th
Saturday, April 18th

but some Easters are changed from the 26th to the 19th by the pyrite rule. Easters changed from the 26th to the 19th are rare, but they are enough to break a tie and make April 19th the most common date for Easter. The second most common date for Easter is the 18th. It's second to the 19th since only some Easters are changed by the pyrite rule from the 25th to the 18th.

Easters between March 28th and April 17th are about equally common, since each of these dates has a full set of seven possible Paschal Full Moons. (They aren't exactly equal since as it turns out, some dates are more likely to fall on Sunday in the Gregorian Calendar than other dates.)

Easters before March 28th or after April 19th are rare, since these extreme Easters have fewer possible Paschal Full Moons. They become decreasingly rare as we approach the extreme dates on either side, March 22nd and April 25th. The rarest Easter of all is March 22nd and not April 25th, since once again, March 21st might be silver, whereas April 18th is always either golden or pyrite.

In the current century, Easter on April 24th occurs twice -- 2011 and 2095. Easter on April 23rd occurs in both 2000 and 2079. Easter on April 22nd occurs in both 2057 and 2068. And this year is the first of four years in this century with an April 21st Easter (2030, 2041, 2052). There are five possible Paschal Full Moons for an April 21st Easter:

Sunday, April 14th
Monday, April 15th
Tuesday, April 16th
Wednesday, April 17th
Thursday, April 18th

And only one of them is completely silver this century, the 15th. This is why it's so much easier to find late Easters this century than early Easters.

The Exceptional Years 1981, 2000, 2019

The three years 1981, 2000, and 2019 are clearly exceptional years when it comes to calculating the date of Easter. We see that 1981 was a year when Easter would have fallen on April 26th had it not been for the pyrite rule. One Metonic Cycle later was 2000, when Easter was also especially late (falling on April 23rd). And one more Metonic Cycle later is this year, when the Gregorian and Aleppo rules produce different dates for Easter.

The reason for all of this is the fact that in all three years, a full moon occurs especially close to the spring equinox. In my discussion of the David Lunar Calendar (December 28th post), I wrote that in the years preceding these three Easters (1980, 1999, 2018), a full moon also occurred around the winter solstice.

Now is a good time to distinguish between "solar months" and "lunar months." A lunar month is simply a lunation -- the time from one moon to the next. On the Chinese Calendar the lunations run from new moon to new moon, whereas for Easter our focus is on full moons.

Now as defined on the Chinese Calendar, a solar month is the time it takes the earth to complete exactly 1/12 of its orbit around the sun. Twelve solar months is exactly one year, whereas twelve lunar months are about 11 days shy of a year. Therefore on average, a lunar month is shorter than a solar month.

But the earth's orbit is elliptical, and so Kepler's Laws tell us that the solar months are shorter when the earth is closer to the sun (perihelion in January) and longer when the earth is farther from the sun (aphelion in July). This explains why the Chinese Calendar rarely has Leap Months after the first or last month of the year. In the winter, the lunar and solar months are about the same length, whereas in summer, the solar months are noticeable longer than the lunar months.

Because of this, the phase of the moon is almost the same at both the winter solstice and the next spring equinox. If there's a full moon at the winter solstice, then the moon at the following spring equinox will also be nearly full. On the other hand, the phase at the following summer solstice will be a waning gibbous moon, at the fall equinox will be a waning half moon (last quarter), and at the winter solstice a year later will be a waning crescent.

All of this tells us that the exceptional winter solstice full moons that I mentioned for the David Lunar Calendar (1980, 1999, 2018) correspond to spring equinox full moons three months later.

We've seen that Aleppo Easter this year is March 24th. But when would Aleppo Easter have fallen in the other two years, 1981 and 2000? Is it possible that Aleppo Easter would have fallen in March in both of those years?

The Webexhibits link from earlier doesn't mention the years 1981 and 2000. After all, Aleppo Easter wasn't even proposed until 1997 and not scheduled to be implemented until 2001. No one is going to build a time machine and go back to 1981 to tell everyone that they were celebrating Easter on the wrong day! This is why links describing the Aleppo Calendar only mention the future. It's only for the interests of creating the David Lunar Calendar where 1980-1981 becomes the Year 0 that we're suddenly interested in full moons from that year.

But here's a link to a webpage created in 1997. The author lists all Aleppo Easters starting from that year and extending to 2205. Thus it includes Aleppo Easter 2000:

http://www.moonwise.co.uk/neweaster.php

According to this link, Gregorian Easter 1998 was on April 12th but Aleppo Easter, had it existed, would have fallen on the 19th instead. It states that while the Paschal Full Moon that year was on April 11th, the full moon in Jerusalem was 45 minutes after midnight on Sunday the 12th, thus forcing Easter to be a week later. But Gregorian and Aleppo Easter do agree in 2000 -- the March full moon that year was definitely before the equinox.

This suggests that the same probably happened in 1981 as well -- the full moon was before the equinox, and so Easter was correctly celebrated in April. What the chart doesn't tell us is whether the full moon fell on Saturday the 18th or Sunday the 19th. If the latter, then Aleppo Easter would have fallen on April 26th -- a date forbidden on the Gregorian Calendar by the pyrite rule.

Looking at the chart at the Moonwise link some more, we see that an April 26th Aleppo Easter is definitely possible. Near the bottom, we see Aleppo Easter on April 26th, 2201. Indeed, the link gives the following line:

The range of dates for the years around now is ... 22 March to 26 April (for a few centuries ahead*) for the astronomical [Aleppo -- dw] definition.

If this chart had extended all the way up to 2877, then March 21st would have appeared. Therefore it appears that the full range of dates for Aleppo Easter is March 21st-April 26th.

Calendar Reform and Easter

Since Aleppo Easter is based on astronomy, no rule-based Calendar Reform will make Easter always fall on the astronomically correct date. But some rules can come close. I've mentioned the Archetypes Calendar, a rule-based calendar that nonetheless seems to match astronomical Chinese New Year:

https://www.hermetic.ch/cal_stud/arch_cal/arch_cal.htm

Still, it's interesting to look at the various proposed calendars to see what Easter looks like on various rule-based calendar.

Of course, this doesn't refer to calendars which seek to fix Easter to a particular date (that is, ignore the moon completely). For example, on the World Calendar, it's sometimes suggested that Easter be fixed to April 8th. (Notice that this is exactly the midpoint of the Gregorian March 22nd-April 25th range as well as the Aleppo March 21st-April 26th range.)

For today's post, our focus is on lunisolar calendars. Not all of these calendars define an Easter, but an Easter is implied if the spring equinox and full moons can be determined from the calendar.

For example, we look at the Meyer-Palmen Solilunar Calendar (named for its two creators):

https://www.hermetic.ch/cal_stud/nlsc/nlsc.htm

On this calendar, the first month, Aristarchus, is supposed to start on the new moon closest to the spring equinox. Thus the full moon of Aristarchus should be the full moon after the equinox. If Aristarchus 1st is a new moon, then the full moon would be around Aristarchus 15th. So we can define the Paschal Full Moon to be Aristarchus 15th, and so Easter is implied to be the following Sunday in the Aristarchus 16th-22nd range. (This calendar doesn't define days of the week, so we can assume that Sundays are the same as on the Gregorian Calendar.)

It may be a complicated, but interesting, exercise to determine "Easter" on this calendar using the definition given above. How often during, say, the current 60-year cycle does "MPSLC Easter" agree with Gregorian or Aleppo Easter?

Suppose we wanted to create a new calendar that agrees with Aleppo Easter as closely as a rule-based calendar possibly can. Well, why don't we start with the following link:

https://calendars.fandom.com/wiki/Easter_Calendar

So apparently, on this calendar, Easter is defined to be New Year's Day. It states that years on this calendar are either 50, 51, 54, or 55 weeks. But other than that, nowhere is it mentioned how to divide the year into months or days. (There is a link on this website, but it's dead.)

So let's try to fill in the calendar ourselves. Let's see -- since 50 and 55 are both multiples of five, we'll divide those years into 10 or 11 months of five weeks each. And since 51 and 54 are both multiples of three, we'll divide those years into 17 or 18 months of three weeks each.

This approach works, but the resulting calendar is terrible. How would you celebrate birthdays on this calendar if there are sometimes 10-11 long months and sometimes 17-18 short months? The same is true for holidays -- in fact, the only holiday that's easy to celebrate is Easter itself!

The number of days in this calendar is always divisible by seven, since it always contains a whole number of weeks. So why don't we try dividing it into seven months instead. Then within a given year, all the months have the same length -- either 50, 51, 54, or 55 days each.

While still awkward, this approach is at least more reasonable than the previous one. The seven months at least correspond roughly to seasons (the first month is always spring, the third month is always around summertime, and the last month is always Lent). Those with birthdays in the first month (from Easter to Pentecost) will celebrate them on the same day of the week every year, while those with birthdays in other months will celebrate on different days of the week (with a maximum of four possible days).

The most logical Easter Calendar is one that is lunisolar, since after all, Easter itself is technically a lunisolar holiday. Since Easter occurs around the full moon, each of the 12-13 months should start around a full moon.

But since the first month always starts on Sunday, every month should begin on Sunday -- indeed, the Sunday after the corresponding full moon (just like Easter itself). The resulting calendar would have 12-13 months of 4-5 weeks each.

Since Easter is so complicated to determine, it may be interesting to create our Easter Calendar based on the simplest Easter rule (the Orthodox one) first. A Gregorian Easter Calendar would be a bigger challenge, where we try to fit in the solar/lunar corrections and the pyrite rules. Only afterward would we attempt to create an Easter Calendar that reproduces the Aleppo definition.

By the way, this Easter Calendar may be the first to require checking the following QNTM box:

(x) the lunar month cannot be evenly divided into seven-day weeks

since it's the only proposed lunisolar calendar that attempts to divide lunar months into weeks.

The Lunisolar Dee Calendar

Another way to create a lunisolar calendar is just to consider the solar and lunar parts separately.

We think back to the Dee Calendar. This is mainly proposed as a solar calendar -- there are eight Leap Days every 33 years. This calendar is supposed to fix the spring equinox to a particular date (March 21st, or March 20th in the Dee-Cecil variant) in one particular time zone -- God's Longitude.

But God's Longitude isn't the meridian of Jerusalem (even though that meridian would appear to be a godly location for Christians). Instead, it's on the East Coast of North America. A different Leap Day rule would have to be adopted (still 8/33 years, but different years from Dee/Dee-Cecil would have the Leap Day) if we wish Jerusalem to be the meridian on which it's based.

That takes care of the solar part. As for the lunar part, there actually was a lunar correction as part of Dee's original proposal. I once found this at the Hermetic link above -- but while the Dee Calendar is still listed there, the calendar correction isn't.

Here's the correction -- we combine the solar and lunar corrections into a single correction where the Paschal Full Moon dates (golden and silver) advance by one day every 231 years (whenever Monday, February 29th is followed five years later by Sunday, February 29th).

It's possible to make this fit the Aleppo Easter given above, if this correction occurs at some point between 2000 and 2019. Then the Paschal Full Moon date would be April 19th, 2000, but then advance and wrap around back to March 21st, 2019, thus making today Easter.

That still doesn't match Aleppo Easter for 1998 -- and we can't just advance the full moons one day in 1998 since we'd have to move them back for 2000. But we don't know which years will have Leap Days in this calendar. It's possible that 1998 might have a Leap Day. Then the Paschal Full Moon can still fall on April 11th, but the Leap Day would change this from Saturday to Sunday, thereby forcing Easter to be a week later on April 18th (Gregorian April 19th).

Once again, no rule-based calendar can capture Aleppo Easter perfectly. It's possible that we'll have to advance the full moons again -- but not exactly 231 years later -- in order to match Aleppo Easter.

Easter on David's Lunar Calendar

I haven't completely decided what my goals for David's Lunar Calendar are, and whether Easter should even appear in my calendar.

On one hand, I want David's Lunar Calendar to describe David -- in other words, me. The main lunisolar holiday that I, David, celebrate is Easter -- Gregorian Easter, not Aleppo Easter. Thus David's Lunar Calendar would be similar to the Easter Calendar (Gregorian) described above, where a particular day on the calendar might correspond to Gregorian Easter. If we wish to improve on the Gregorian rule, then it shouldn't happen until long after I leave this world, since the Easters would no longer correspond to dates actually celebrated by me, David.

If this is my goal, then for one thing, New Year's Day on this calendar should be late in the years 0 (1980-1981), 19 (1999-2000), 38 (2018-2019), and so on. The idea was for the first day of the calendar to be my birthday -- December 7th, 1980. This would require the other years to start in the month leading up to my birthday.

Thus most years would start in November, and Easter would fall in the fifth month (Greenlong). It's impossible to make "Easter" always fall on a Sunday, of course, since my days of my 12-day week have nothing to do with the seven-day week. Once again, the idea is just to define the Paschal Full Moon to be, say Greenlong 15th (which would fall on either Violetday or Violetend) -- one would have to retreat to Gregorian days to find the following Sunday.

On the other hand, I might want David's Lunar Calendar to improve on the Gregorian Calendar, so that Greenlong 15th is always the Aleppo Paschal Full Moon. So if Year 19 (1999-2000) starts on December 7th, Year 38 (2018-2019) would start a full month earlier, around November 7th, in order to make Greenlong 15th fall near last week's full moon. This means that a deviation from the Metonic Cycle must occur between Year 19 and Year 38. The rules I stated on January 6th (the date I first posted David's Lunar Calendar) don't do this.

Actually, making a correction between Year 19 and 38 is awkward (especially when the first correction specified on January 6th was for a 57-year correction). It makes more sense to deviate from the Metonic Cycle at either the beginning or end of a larger cycle.

One thing I first noticed about the Meyer-Palmen Solilunar Calendar (or a generalization thereof, which Karl Palmen calls a "YLM calendar") is that the deviation from the Metonic Cycle occurs right at the start. In fact, this is why Year 0 of his calendar starts on the latest possible date, April 8th. The calendar immediately adjusts so that Year 19 starts about a month earlier.

So in order to capture Aleppo Easter, we can declare Year 0 to be 1999-2000 and start the calendar on my birthday, December 7th. Then Year 19 will start around November 7th, and both the late Aleppo Easter in 2000 and the early Aleppo Easter in 2019 fall during the second full week of Greenlong.

(This also allows me to remove my birth year from the calendar, and instead makes Year 0 line up with Gregorian Year 2000, which is convenient.)

Conclusion

Well, I hope that you learned a lot about Easter in this post, my first of two spring break posts. It allows me to return to one of my favorite topics -- calendars -- just ahead of the main lunisolar holiday that I celebrate, Easter, and gives me a chance to use the calendar that I just invented.

I wish everyone a Happy (Aleppo) Easter today!