#include <time.h>
The <time.h> header shall define the clock_t, size_t, time_t, types as described in <sys/types.h>.
The <time.h> header shall define the clockid_t and timer_t types as described in <sys/types.h>.
The <time.h> header shall define the locale_t type as described in <locale.h>.
The <time.h> header shall define the pid_t type as described in <sys/types.h>.
The tag sigevent shall be declared as naming an incomplete structure type, the contents of which are described in the <signal.h> header.
The <time.h> header shall declare the tm structure, which shall include at least the following members:
int tm_sec Seconds [0,60]. int tm_min Minutes [0,59]. int tm_hour Hour [0,23]. int tm_mday Day of month [1,31]. int tm_mon Month of year [0,11]. int tm_year Years since 1900. int tm_wday Day of week [0,6] (Sunday =0). int tm_yday Day of year [0,365]. int tm_isdst Daylight Savings flag.
The value of tm_isdst shall be positive if Daylight Savings Time is in effect, 0 if Daylight Savings Time is not in effect, and negative if the information is not available.
The <time.h> header shall declare the timespec structure, which shall include at least the following members:
time_t tv_sec Seconds. long tv_nsec Nanoseconds.
The <time.h> header shall also declare the itimerspec structure, which shall include at least the following members:
struct timespec it_interval Timer period. struct timespec it_value Timer expiration.
The <time.h> header shall define the following macros:
The <time.h> header shall define the following symbolic constants. The values shall have a type that is assignment-compatible with clockid_t.
The <time.h> header shall define the following symbolic constant:
The <time.h> header shall provide a declaration or definition for getdate_err. The getdate_err symbol shall expand to an expression of type int. It is unspecified whether getdate_err is a macro or an identifier declared with external linkage, and whether or not it is a modifiable lvalue. If a macro definition is suppressed in order to access an actual object, or a program defines an identifier with the name getdate_err, the behavior is undefined.
The following shall be declared as functions and may also be defined as macros. Function prototypes shall be provided.
char *asctime(const struct tm *);
char *asctime_r(const struct tm *restrict, char *restrict);
clock_t clock(void);
int clock_getcpuclockid(pid_t, clockid_t *);
int clock_getres(clockid_t, struct timespec *);
int clock_gettime(clockid_t, struct timespec *);
int clock_nanosleep(clockid_t, int, const struct timespec *,
struct timespec *);
int clock_settime(clockid_t, const struct timespec *);
char *ctime(const time_t *);
char *ctime_r(const time_t *, char *);
double difftime(time_t, time_t);
struct tm *getdate(const char *);
struct tm *gmtime(const time_t *);
struct tm *gmtime_r(const time_t *restrict, struct tm *restrict);
struct tm *localtime(const time_t *);
struct tm *localtime_r(const time_t *restrict, struct tm *restrict);
time_t mktime(struct tm *);
int nanosleep(const struct timespec *, struct timespec *);
size_t strftime(char *restrict, size_t, const char *restrict,
const struct tm *restrict);
size_t strftime_l(char *restrict, size_t, const char *restrict,
const struct tm *restrict, locale_t);
char *strptime(const char *restrict, const char *restrict,
struct tm *restrict);
time_t time(time_t *);
int timer_create(clockid_t, struct sigevent *restrict,
timer_t *restrict);
int timer_delete(timer_t);
int timer_getoverrun(timer_t);
int timer_gettime(timer_t, struct itimerspec *);
int timer_settime(timer_t, int, const struct itimerspec *restrict,
struct itimerspec *restrict);
void tzset(void);
The <time.h> header shall declare the following as variables:
extern int daylight; extern long timezone; extern char *tzname[];
Inclusion of the <time.h> header may make visible all symbols from the <signal.h> header.
The following sections are informative.
tm_year is a signed value; therefore, years before 1900 may be represented.
To obtain the number of clock ticks per second returned by the times() function, applications should call sysconf(_SC_CLK_TCK).
The System Interfaces volume of POSIX.1-2017, Section 2.2, The Compilation Environment, asctime(), clock(), clock_getcpuclockid(), clock_getres(), clock_nanosleep(), ctime(), difftime(), getdate(), gmtime(), localtime(), mktime(), mq_receive(), mq_send(), nanosleep(), pthread_getcpuclockid(), pthread_mutex_timedlock(), pthread_rwlock_timedrdlock(), pthread_rwlock_timedwrlock(), sem_timedwait(), strftime(), strptime(), sysconf(), time(), timer_create(), timer_delete(), timer_getoverrun(), tzset(), utime()
Any typographical or formatting errors that appear in this page are most likely to have been introduced during the conversion of the source files to man page format. To report such errors, see https://www.kernel.org/doc/man-pages/reporting_bugs.html .