#define TM_YEAR_BASE 1900
verify (base_year_is_a_multiple_of_100, TM_YEAR_BASE % 100 == 0);
-#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
+/* Return 1 if YEAR + TM_YEAR_BASE is a leap year. */
+static inline int
+leapyear (int year)
+{
+ /* Don't add YEAR to TM_YEAR_BASE, as that might overflow.
+ Also, work even if YEAR is negative. */
+ return
+ ((year & 3) == 0
+ && (year % 100 != 0
+ || ((year / 100) & 3) == (- (TM_YEAR_BASE / 100) & 3)));
+}
/* How many days come before each month (0-12). */
#ifndef _LIBC
/* Calculate day of year from year, month, and day of month.
The result need not be in range. */
- int yday = ((__mon_yday[__isleap (year + TM_YEAR_BASE)]
+ int yday = ((__mon_yday[leapyear (year)]
[mon_remainder + 12 * negative_mon_remainder])
+ mday - 1);