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Annotation of coherent/g/usr/lib/misc/jdtotm.c, revision 1.1.1.1

1.1       root        1: /*
                      2:  * Julian date to year, month, mday, hour, min, sec, yday, wday fields
                      3:  * Algorithm from Duffett-Smith, Practical Astronomy With Your Calculator
                      4:  * Also Meeus, Astronomical Formulae for Calculators
                      5:  */
                      6: #include "local_misc.h"
                      7: tm_t *
                      8: jday_to_tm(jd)
                      9: jday_t jd;
                     10: {
                     11:        register tm_t *tp;
                     12:        register long d, s, A, B, F;
                     13:        static tm_t t;
                     14: 
                     15:        tp = &t;
                     16:        d = jd.j_d;
                     17:        s = jd.j_s;
                     18:        if ((s += 86400L/2) >= 86400L) {
                     19:                s -= 86400L; d += 1;
                     20:        }
                     21:        tp->tm_isdst = 0;               /* no telling who stepped here */
                     22:        tp->tm_wday = (d+1) % 7;
                     23:        if ((A = d) > 2299160L) {
                     24:                A = (d*100 - 186721625L) / 3652425L;
                     25:                A = d + 1 + A - (A / 4);
                     26:        }
                     27:        B = A + 1524;
                     28:        tp->tm_year = (B*100 - 12210) / 36525L;
                     29:        B -= (tp->tm_year * 36525L) / 100;
                     30:        tp->tm_mon = (B * 10000) / 306001L;
                     31:        F = (306001L * tp->tm_mon) / 10000;
                     32:        tp->tm_mday = B - F;
                     33:        tp->tm_yday = B - (tp->tm_mon >= 14 ? 428+1 : 61+2+1);
                     34:        tp->tm_mon -= tp->tm_mon > 13 ? 13 : 1;
                     35:        tp->tm_year -= tp->tm_mon > 2 ? 4716 :  4715;
                     36:        if (tp->tm_mon > 2 && isleapyear(tp->tm_year))
                     37:                ++tp->tm_yday;
                     38:        tp->tm_sec = s % 60;
                     39:        s /= 60;
                     40:        tp->tm_min = (unsigned int)s % 60;
                     41:        tp->tm_hour = (unsigned int)s / 60;
                     42:        /* Correct for tm_t bias */
                     43:        tp->tm_year -= 1900;
                     44:        tp->tm_mon -= 1;
                     45:        return tp;
                     46: }

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