1 files changed, 33 insertions, 0 deletions
diff --git a/src/time/__tm_to_time.c b/src/time/__tm_to_time.c
new file mode 100644
index 00000000..3fa15fad
--- /dev/null
+++ b/src/time/__tm_to_time.c
@@ -0,0 +1,33 @@
+#include <time.h>
+
+/* C defines the rounding for division in a nonsensical way */
+#define Q(a,b) ((a)>0 ? (a)/(b) : -(((b)-(a)-1)/(b)))
+
+time_t __tm_to_time(struct tm *tm)
+{
+	time_t year  = tm->tm_year + -100;
+	int    month = tm->tm_mon;
+	int    day   = tm->tm_mday;
+	int z4, z100, z400;
+
+	/* normalize month */
+	if (month >= 12) {
+		year += month/12;
+		month %= 12;
+	} else if (month < 0) {
+		year += month/12;
+		month %= 12;
+		if (month) {
+			month += 12;
+			year--;
+		}
+	}
+	z4 = Q(year - (month < 2), 4);
+	z100 = Q(z4, 25);
+	z400 = Q(z100, 4);
+	day += year*365 + z4 - z100 + z400 +
+		month[(int []){0,31,59,90,120,151,181,212,243,273,304,335}];
+	return (long long)day*86400
+		+ tm->tm_hour*3600 + tm->tm_min*60 + tm->tm_sec
+		- -946684800; /* the dawn of time :) */
+}