glibc/include/time.h

#ifndef _TIME_H
#if defined __need_time_t  || defined __need_clock_t || defined __need_timespec
# include <time/time.h>
#else
# include <time/time.h>

/* Now define the internal interfaces.  */
struct tm;

/* Defined in mktime.c.  */
extern const unsigned short int __mon_yday[2][13];

/* Defined in localtime.c.  */
extern struct tm _tmbuf;

/* Defined in tzset.c.  */
extern char *__tzstring __P ((const char *string));

/* Defined in tzset.c. */
extern size_t __tzname_cur_max;


extern int __use_tzfile;

extern void __tzfile_read __P ((const char *file, size_t extra,
				char **extrap));
extern int __tzfile_compute __P ((time_t timer, int use_localtime,
				  long int *leap_correct, int *leap_hit,
				  struct tm *tp));
extern void __tzfile_default __P ((const char *std, const char *dst,
				   long int stdoff, long int dstoff));

/* Subroutine of `mktime'.  Return the `time_t' representation of TP and
   normalize TP, given that a `struct tm *' maps to a `time_t' as performed
   by FUNC.  Keep track of next guess for time_t offset in *OFFSET.  */
extern time_t __mktime_internal __P ((struct tm *__tp,
				      struct tm *(*__func) (const time_t *,
							    struct tm *),
				      time_t *__offset));
extern struct tm *__localtime_r __P ((__const time_t *__timer,
				      struct tm *__tp));

/* Compute the `struct tm' representation of *T,
   offset OFFSET seconds east of UTC,
   and store year, yday, mon, mday, wday, hour, min, sec into *TP.
   Return nonzero if successful.  */
extern int __offtime __P ((__const time_t *__timer,
			   long int __offset,
			   struct tm *__tp));

extern char *__asctime_r __P ((__const struct tm *__tp, char *__buf));
extern void __tzset __P ((void));

/* Prototype for the internal function to get information based on TZ.  */
extern struct tm *__tz_convert __P ((const time_t *timer, int use_localtime, struct tm *tp));

/* Return the maximum length of a timezone name.
   This is what `sysconf (_SC_TZNAME_MAX)' does.  */
extern long int __tzname_max __P ((void));

extern int __nanosleep __P ((__const struct timespec *__requested_time,
			     struct timespec *__remaining));
extern int __getdate_r __P ((__const char *__string, struct tm *__resbufp));
#endif
#endif