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yap-6.3/packages/PLStream/libtai/caldate_mjd.c

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2010-07-19 14:52:26 +01:00
#include "tai.h"
#include "caldate.h"
static unsigned long times365[4] = { 0, 365, 730, 1095 } ;
static unsigned long times36524[4] = { 0, 36524UL, 73048UL, 109572UL } ;
static unsigned long montab[12] =
{ 0, 31, 61, 92, 122, 153, 184, 214, 245, 275, 306, 337 } ;
/* month length after february is (306 * m + 5) / 10 */
long caldate_mjd(struct caldate *cd)
{
long y;
long m;
long d;
d = cd->day - 678882L;
m = cd->month - 1;
y = cd->year;
d += 146097L * (y / 400);
y %= 400;
if (m >= 2) m -= 2; else { m += 10; --y; }
y += (m / 12);
m %= 12;
if (m < 0) { m += 12; --y; }
d += montab[m];
d += 146097L * (y / 400);
y %= 400;
if (y < 0) { y += 400; d -= 146097L; }
d += times365[y & 3];
y >>= 2;
d += 1461L * (y % 25);
y /= 25;
d += times36524[y & 3];
return d;
}