C Tutorial/time.h/Introduction

Time, Date, and Localization Functions

1. The time and date functions are defined in the header .
2. This header defines three time-related types: clock_t, time_t, and tm.
3. The types clock_t and time_t represent the system time and date.
4. This is called the calendar time.

The tm structure contains the following members:

<source lang="cpp">int tm_sec; /* seconds, 0-60 */

 int tm_min;  /* minutes, 0-59 */
 int tm_hour; /* hours, 0-23 */
 int tm_mday; /* day of the month, 1-31 */
 int tm_mon;  /* months since Jan, 0-11 */
 int tm_year; /* years from 1900 */
 int tm_wday; /* days since Sunday, 0-6 */
 int tm_yday; /* days since Jan 1, 0-365 */
 int tm_isdst /* Daylight Saving Time indicator */</source>

tm_isdst is positive during daylight saving time, zero if it not, and negative if there is no information available.

This form of the time and date is called the broken-down time.

In addition, defines the macro CLOCKS_PER_SEC, which is the number of system clock ticks per second.

The geopolitical environmental functions require the header <locale.h>. It defines the structure lconv, which is described under the function localeconv().