Last change
on this file since 0170798 was 3ae31e9, checked in by Thomas Lopatic <thomas@…>, 7 years ago |
Imported original source code.
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100755
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File size:
1.1 KB
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[3ae31e9] | 1 | /*
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| 2 | =============================================================================
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| 3 | jday.c -- convert date to Julian day. -- ACM algorithm 199
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| 4 |
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| 5 | A Julian day is the number of days since some base date
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| 6 | in the very distant past.
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| 7 |
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| 8 | Handy for getting date of x number of days after a given Julian date
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| 9 | Use jdate() to get that from the Gregorian date.
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| 10 |
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| 11 | Written by: Robert G. Tantzen
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| 12 |
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| 13 | Translated to C by: Nat Howard
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| 14 |
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| 15 | Revised by: D.N. Lynx Crowe
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| 16 | 1998-01-14 -- optimized for speed
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| 17 |
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| 18 | Translated from the algol original in Collected Algorithms of the <ACM
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| 19 | This and jdate() are algorithm 199.
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| 20 | =============================================================================
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| 21 | */
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| 22 |
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| 23 | long
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| 24 | jday(mon, day, year)
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| 25 | int mon, day, year;
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| 26 | {
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| 27 | register long y = year;
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| 28 | register long m = mon;
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| 29 | register long j;
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| 30 | register long ya;
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| 31 | register long c;
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| 32 | long d = day;
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| 33 |
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| 34 | if(m > 2) {
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| 35 |
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| 36 | m -= 3L;
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| 37 |
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| 38 | } else {
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| 39 |
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| 40 | m += 9L;
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| 41 | --y;
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| 42 | }
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| 43 |
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| 44 | c = y / 100L;
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| 45 | ya = y - (100L * c);
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| 46 |
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| 47 | j = (146097L * c) / 4L
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| 48 | + (1461L * ya) / 4L
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| 49 | + (153L * m + 2L) / 5L
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| 50 | + d + 1721119L;
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| 51 |
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| 52 | return(j);
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| 53 | }
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