When is Easter?

An explanation of the date of Easter, and why it changes every year.

Intro and outro music is my original arrangement of "House of the Rising Sun".
Thanks to Theo Aldridge-Stone for checking out the script.

00:00 Intro
00:38 The Sun and the Moon
03:58 The Hebrew Calendar
05:54 The First Council of Nicaea
07:25 The Lies
10:31 Conclusion

IMAGE CREDITS

(All images are licensed under CC BY-SA 3.0)

SOURCES

#easter #2023

[KieranBorovac]

THIS YEAR: Easter 2024 is on the 31st of March.

CORRECTIONS:
- The diagram at 7:43 is misleading; a more accurate reflection of the orbital mechanics would have the earth tilted at the same angle, but rotating *around the sun* until the tilt is perpendicular. Unfortunately I am not good enough at 3D graphics to properly illustrate this.
- I wrote "21 March" at 10:25 when I should have written "21 April"

[garyfrancis]

I use the Candy Calendar. Easter is three months after the Easter eggs show up in the stores. It’s pretty accurate.

[SingABrightSong]

Friend of mine did Y2K testing back in 1999 or so and she mentioned that she was far more likely to crash a database, rather than by setting the date to January 1, 2000, setting it to February 29th. The Gregorian calendar reforms add a leap day every four years, except for every hundredth year, but there's an exception to that exception every four hundred years which many programmers were unaware of, so the very real date of February 29th 2000 threatened a range of important software.

[maverick_monkey]

I see that the most crucial compliments have already been delivered, so I’ll just give an enthusiastic thumbs up for that lovely House of the Rising Sun intro and outro!

[strider_hiryu]

the fact that Apollonios of Perga figured out the perfect calendar when he created what is now called the Antikythera Mechanism, twenty two hundred years ago is wildly impressive

[PanglossDr]

This was really interesting.

It reminded me of a number of Laws in Physics and Chemistry like Avogadro's Law which are commonly misquoted because they should be followed by the phrase 'at standard temperature and pressure'.

The full definition for the date of Easter should be 'The first Sunday after the full Moon that occurs on or after the Spring Equinox, based on specific definitions of Equinox and Full Moon'.

[GregPerham]

"Determining your position in a solar cycle requires specialized equipment" *Stonehenge* Literally lol 😆

[thedreamorb]

"The ripeness of barley is not a precise astronomical measurement" is honestly a banger quote

[pierremainstone-mitchell]

My late dad was an Anglican (Episcopalian) Priest and I remember amusing myself from time to time reading the pages in the Anglican (1662) Prayer Book detailing how to find the date of Easter and I could never really get mt head around it! Glad to see that I'm not alone in this!

Btw - I roared with laughter at your comment about working out where you are in the Solar calendar requiring specialized equipment with a quick visual of Stonehenge! Nice one indeed!

[lonnieporter]

Your "House of the Rising Sun" arrangement is freaking killer!
Love it, man; well done!

[timothybarnett]

Alternatively the is the UK Parliament 1928 Easter Act that establishes Easter Sunday as the Sunday following the second Saturday in April, resulting in Easter Sunday being between 9 April and 15 April. It's never been enforced.

[goskascience]

10:27 The last (bottom right) date should be Sun 21 *Apr*, right?

[bearcubdaycare]

It's interesting that Christmas (birth of Christ) can just always be December 25, but Good Friday and Easter (death and resurrection of Christ) need a complicated formula. It raises the question of why not just pick a fixed date for Easter relative to the calendar, like for Christmas.

[betaneptune]

Of course, the easiest way to determine the date of Easter is the following: Get yourself a calendar. Look for Easter in March and April. Whatever it says there, that's the date!

[occamraiser]

Fun fact: The formula for deciding on the date of Easter was decided in an international meeting (Synod of Whitby) in the 7th Century. The same Whitby that Dracula landed at and who's Abbey/Graveyard he took up residence.
Frankly, Whitby is more well known for fictional Dracula than for it's contribution to the Western World's ecclesiastical calendar :)

[alloydog]

That ran like the intro to the old TV comedy, "Soap"! I was half expecting you to end with "Confused? You will be!" :D

[gunlovingliberal]

The piano playing House of the Rising Sun at the end was a great touch. 👍👍👍👍👍

[thevikingbear]

I use the Target calendar. Easter is the day I go grocery shopping and Target is closed. Works every year!

[friedlotto]

This complied beautifully with the BBC’s charter: to inform, educate and entertain.

It also reminded me of Zain Rizvi’s delightful post entitled “Falsehoods programmers believe about time zones”, which I suspect @Kieran Borovac and anyone who enjoys his excellent content will find informative, educational and entertaining.

[nowster]

The default daylight savings change date rule in the UK used to be "the Sunday after the fourth Saturday of March and October unless that Sunday is Easter in which case it will be the Sunday after". In practice the default rule was almost never invoked, with the dates being set by Statutory Instrument each year, except for a few times when that didn't happen.

EU harmonization in the late 1990s fixed that to the more simple last Sunday in March/October rule we have now.