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

Text File | 1994-05-12 | 932 b | 32 lines

#    Calculate the calendar date (month, day, year) corresponding to
#    a Julian day number.  (Negative years are B.C.)
#    Based on algorithms published in Computer Language magazine,
#    December, 1990.  Used with permission.

proc caldate(jdate)
    local a, b, c, d, e, z, alpha, month, day, year
    set month = January February March April May June ^
        July August September October November December
    @ z = jdate + 1
    # Cope with the Gregorian calendar reform.
    if (z < 2299161) then
        @ a = z
        # Intercept years B.C.
        if (z < 1721423) @ a -= 366
    else
        @ alpha = (z - 1867216.25)//36524.25
        @ a = z + 1 + alpha - alpha//4
    end
    @ b = a + 1524
    @ c = (b - 122.1)//365.25
    @ d = floor(365.25 * c)
    @ e = (b - d)//30.6001
    @ day = b - d - floor(30.6001 * e)
    @ e -= e < 14 ? 2 : 14
    @ month = month[e]
    if ((year = e > 1 ? c - 4716 : c - 4715) == 0) @ year--
    return "$month $day $year"
end

caldate $argv