Piper's Pit BBS/FTP: ibm 0210 - 0219/ibm0210-0219/ibm0213.tar/ibm0213/HAM_W32.ZIP/SAMPLES/EASTER.CSH

Text File | 1994-05-12 | 1.0 KB | 34 lines

#    Calculate when Easter will occur in any given year.
#    Copyright (c) 1991 by Hamilton Laboratories.  All rights reserved.

proc easter (year)
    local a, b, c, d, e, f, g, h, i, k, l, m, n, month, day
    set month = January February March April May June ^
        July August September October November December
    if (year == "") @ year = `date`:3
    if (year >= 1583) then
        # Gregorian calendar
        @ a = year % 19;  @ b = year // 100;  @ c = year % 100
        @ d = b // 4;  @ e = b % 4;  @ f = (b + 8) // 25
        @ g = (b - f + 1) // 3
        @ h = (19 * a + b - d - g + 15) % 30
        @ i = c // 4;  @ k = c % 4
        @ l = (32 + 2 * e + 2 * i - h - k) % 7
        @ m = (a + 11 * h + 22 * l) // 451
        @ n = h + l - 7 * m + 114
        @ month = month[n // 31 - 1]
        @ day = n % 31 + 1
    else
        # Julian calendar
        @ a = year % 4;  @ b = year % 7;  @ c = year % 19;
        @ d = (19 * c + 15) % 30
        @ e = (2 * a + 4 * b - d + 34) % 7
        @ f = d + e + 114
        @ month = month[f // 31 - 1]
        @ day = f % 31 + 1
    end
    return "$month $day $year"
end

easter $argv