#include "datetime.h"

/* roughly 100x faster than mktime() */
datetime_sec datetime_untai(dt)
struct datetime *dt;
{
 int year;
 int day;
 int mon;

 year = dt->year + 1900;

 mon = dt->mon;
 if (mon >= 2) { mon -= 2; }
 else { mon += 10; --year; }

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

 if (day == 365) { year -= 3; day = 1460; }
 else { day += 365 * (year % 4); }
 year /= 4;

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

 if (day == 36524) { year -= 3; day = 146096; }
 else { day += 36524 * (year % 4); }
 year /= 4;

 day += 146097 * (year - 5);
 day += 11017;

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