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Comment by te_platt | Hacker News Reader

I'm always curious when Gauss turns up in the solution to a math problem. Wikipedia has a section on the algorithm here: https://en.wikipedia.org/wiki/Computus#Gauss_algorithm

The same article also explains why it is a hard problem:

"Easter calculations are based on agreements and conventions, not on the actual celestial movements nor on indisputable facts of history."

Sounds a lot like many user requirements I have had to code for.

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Reminds me of the comment in a time zone file:

  From: Jonathan Leffler
  # [British Summer Time] is fixed annually by Act of Parliament.
  # If you can predict what Parliament will do, you should be in
  # politics making a fortune, not computing.

https://github.com/lattera/glibc/blob/master/timezone/europe

Astronomically derived Easter is the Sunday after the full moon after the vernal equinox, and that's quite easy to calculate. I thought of implementing Computus, but gave up as it's so arbitrary that nothing worthwhile would be learned by implementing it. I implemented astronomical Easter instead, knowing that it's occasionally wrong: http://web.onetel.com/~hibou/fmj/tutorials/GregorianCalendar... - scroll down to Bell, Book, and Candle.

This was my first programming assignment (7th grade math class, 1975). It was a great introduction to computers and algorithms. I think I still have that BASIC program on a paper tape in my basement.

I like your writing style and went to your website to look for a blog., but it's down[1]

[1] http://www.downforeveryoneorjustme.com/www.tracyplatt.com

The agreements and conventions make it easier, not harder, than something based on celestial movements.

The earth's rotation changes by unpredictable amounts, so it would be impossible to predict in advance purely based on celestial movements.

Gauss's algorithm was also used in an IOCCC entry: http://ioccc.org/years.html#1996_schweikh1

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