1 files changed, 53 insertions, 0 deletions
diff --git a/src/datetime.c b/src/datetime.c
new file mode 100644
index 0000000..3db5f7f
--- /dev/null
+++ b/src/datetime.c
@@ -0,0 +1,53 @@
+/* 19950925 */
+#include "datetime.h"
+
+void datetime_tai(struct datetime *dt,datetime_sec t)
+{
+  int day;
+  int tod;
+  int year;
+  int yday;
+  int wday;
+  int mon;
+ 
+  tod = t % 86400;
+  day = t / 86400;
+  if (tod < 0) { tod += 86400; --day; }
+ 
+  dt->hour = tod / 3600;
+  tod %= 3600;
+  dt->min = tod / 60;
+  dt->sec = tod % 60;
+ 
+  wday = (day + 4) % 7; if (wday < 0) wday += 7;
+  dt->wday = wday;
+ 
+  day -= 11017;
+  /* day 0 is march 1, 2000 */
+  year = 5 + day / 146097;
+  day = day % 146097; if (day < 0) { day += 146097; --year; }
+  /* from now on, day is nonnegative */
+  year *= 4;
+  if (day == 146096) { year += 3; day = 36524; }
+  else { year += day / 36524; day %= 36524; }
+  year *= 25;
+  year += day / 1461;
+  day %= 1461;
+  year *= 4;
+  yday = (day < 306);
+  if (day == 1460) { year += 3; day = 365; }
+  else { year += day / 365; day %= 365; }
+  yday += day;
+ 
+  day *= 10;
+  mon = (day + 5) / 306;
+  day = day + 5 - 306 * mon;
+  day /= 10;
+  if (mon >= 10) { yday -= 306; ++year; mon -= 10; }
+  else { yday += 59; mon += 2; }
+ 
+  dt->yday = yday;
+  dt->year = year - 1900;
+  dt->mon = mon;
+  dt->mday = day + 1;
+}