- time_t tl, tb;
- struct tm *tg;
-
- tl = mktime (t);
- if (tl == -1)
- {
- t->tm_hour--;
- tl = mktime (t);
- if (tl == -1)
- return -1; /* can't deal with contents of T */
- tl += 3600;
- }
- tg = gmtime (&tl);
- tg->tm_isdst = 0;
- tb = mktime (tg);
- if (tb == -1)
- {
- tg->tm_hour--;
- tb = mktime (tg);
- if (tb == -1)
- return -1; /* can't deal with output from gmtime */
- tb += 3600;
- }
- return (tl - (tb - tl));
+ static const unsigned short int month_to_days[][13] = {
+ { 0, 31, 59, 90, 120, 151, 181, 212, 243, 273, 304, 334 },
+ { 0, 31, 60, 91, 121, 152, 182, 213, 244, 274, 305, 335 }
+ };
+ unsigned long secs;
+ int year, days;
+
+ /* Only handles years between 1970 and 2099. */
+ if (t->tm_year < 70 || t->tm_year > 129)
+ return (time_t) -1;
+
+ days = 365 * (t->tm_year - 70);
+ /* Take into account the leap days between 1970 and YEAR-1; all
+ years divisible by four between 1968 and 2100 should be leap. */
+ days += (t->tm_year - 1 - 68) / 4;
+ if (t->tm_mon < 0 || t->tm_mon >= 12)
+ return (time_t) -1;
+ days += month_to_days[IS_LEAP (1900 + t->tm_year)][t->tm_mon];
+ days += t->tm_mday - 1;
+
+ secs = days * 86400 + t->tm_hour * 3600 + t->tm_min * 60 + t->tm_sec;
+ return (time_t) secs;