Easter Holiday formulas -- How do they do it!? [low priority post]

Steve Kunkel · #1 11-10-2022, 02:41 PM

Attached is a group of formulas for US holidays that I found on the web a long time ago. (Though I did write the DST ones myself

)

I've found 2 different formulas (on the web) that will calculate Easter.

Code:

=DOLLAR(("4/"&theyear)/7+MOD(19*MOD(theyear,19)-7,30)*14%,)*7-6
=ROUND(DATE(theyear,4,MOD(234-11*MOD(theyear,19),30))/7,0)* 7-6

I'm just curious if anyone here created either of these... I'm wondering: What method does a person even use to write one of these?

Something like "the second Sunday of March" can be systematically figured out, since there are only 7 possible permutations of what a "March" month can look like... But Easter is based on the full moon! As I found on the web:

Quote:

The simple standard definition of Easter is that it is the first Sunday after the full Moon that occurs on or after the spring equinox. If the full Moon falls on a Sunday then Easter is the next Sunday.

The only thing I can figure, is that these were somehow "reverse-engineered." I have no idea how that would be done though...

I hand-checked for the next 10 Easters, and both of these formulas appeared to yield correct results...

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