+
+#ifndef __isleap
+/* Nonzero if YEAR is a leap year (every 4 years,
+ except every 100th isn't, and every 400th is). */
+# define __isleap(year) \
+ ((year) % 4 == 0 && ((year) % 100 != 0 || (year) % 400 == 0))
+#endif
+
+/* Compute the day of the week. */
+static void
+day_of_the_week (struct tm *tm)
+{
+ /* We know that January 1st 1970 was a Thursday (= 4). Compute the
+ the difference between this data in the one on TM and so determine
+ the weekday. */
+ int corr_year = 1900 + tm->tm_year - (tm->tm_mon < 2);
+ int wday = (-473
+ + (365 * (tm->tm_year - 70))
+ + (corr_year / 4)
+ - ((corr_year / 4) / 25) + ((corr_year / 4) % 25 < 0)
+ + (((corr_year / 4) / 25) / 4)
+ + __mon_yday[0][tm->tm_mon]
+ + tm->tm_mday - 1);
+ tm->tm_wday = ((wday % 7) + 7) % 7;
+}
+
+/* Compute the day of the year. */
+static void
+day_of_the_year (struct tm *tm)
+{
+ tm->tm_yday = (__mon_yday[__isleap (1900 + tm->tm_year)][tm->tm_mon]
+ + (tm->tm_mday - 1));
+}
+