skip@rafos.gso.uri.edu (Skip Carter) (06/07/90)
Here is how to calculate the date of Easter for ANY YEAR in the Gregorian Calendar (i.e. after 1583), no exceptions. The algorithm is particulary well suited to Forth because of the /MOD operator. This is from the book: Astronomical Formulae for Calculators, by Jean Meeus, Published in 1982 by Willman-Bell Inc. Divide by Quotient Remainder the year x 19 --- a the year x 100 b c b 4 d e b + 8 25 f --- b - f + 1 3 g --- 19a + b - d - g + 15 30 --- h c 4 i k 32 + 2e + 2i - h - k 7 --- L a + 11h + 22L 45L m --- h + L - 7m + 114 31 n p Then n = the number of the month (3 = March, 4 = April) p+1 = day of the month upon which Easter Sunday falls. Test cases: 1978 -> March 26 1954 -> April 18 1979 -> April 15 2000 -> April 23 1980 -> April 6 Skip Carter UUCP: uunet!rafos!skip School of Oceanography INTERNET: skip@rafos.gso.uri.edu University of Rhode Island Phone: 401-792-6519 Narragansett, RI 02882