1 #include "datetime.h"

     2 

     3 /* roughly 100x faster than mktime() */

     4 datetime_sec datetime_untai(dt)

     5 struct datetime *dt;

     6 {

     7   int year;

     8   int day;

     9   int mon;

    10  

    11   year = dt->year + 1900;

    12  

    13   mon = dt->mon;

    14   if (mon >= 2) { mon -= 2; }

    15   else { mon += 10; --year; }

    16  

    17   day = (dt->mday - 1) * 10 + 5 + 306 * mon;

    18   day /= 10;

    19  

    20   if (day == 365) { year -= 3; day = 1460; }

    21   else { day += 365 * (year % 4); }

    22   year /= 4;

    23  

    24   day += 1461 * (year % 25);

    25   year /= 25;

    26  

    27   if (day == 36524) { year -= 3; day = 146096; }

    28   else { day += 36524 * (year % 4); }

    29   year /= 4;

    30  

    31   day += 146097 * (year - 5);

    32   day += 11017;

    33  

    34   return ((day * 24 + dt->hour) * 60 + dt->min) * 60 + dt->sec;

    35 }