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