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6.2.3.1.2.2.3
easter_julian () |
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This routine (Listing 6.16) returns the date for Western Easter on a given year in the Julian calendar system for dates after A.D. 463. This date is not the Eastern Easter of the Eastern Orthodox churches. |
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6.2.3.1.2.2.4
easter_gregorian_meeus () |
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This Gregorian Easter routine (Listing 6.17) is given by Jean Meeus in his book Astronomical Algorithms. It is valid for all Gregorian years; that is, years > 1582. |
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| Listing 6.15 | |
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/* The value of 'e' may be negative. The case of year = 14250, e.g.,
produces values of g = 1, z = 40 and x = 95. The value of el is thus
-24, and the 'mod' code fails to return the proper positive result.
The following correction produces a positive value, mod 30, for 'e'.
*/
while (e < 0L)
e += 30L;
if ( ((e == 25L) && (g > 11)) || (e == 24L) )
e++;
n = 44L - e;
if (n < 21L)
n += 30L;
dpn = d + n;
nl = dpn - ((dpn / 7L) * 7L);
n = n + 7L - nl;
if (n > 31L)
{
date.month = 4;
date.day = (int) (n - 31L);
}
else
{
date.month = 3;
date.day = (int) n;
}
date.year = year;
return (date);
}
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