**Time Manipulation Functions**
|clock        |Clock program                                   |
|difftime     |return difference between two times             |
|mktime       |Convert tm structure to time_t                  |
|time         |Get current time                                |
**Conversion Functions**
|asctime       |Convert tm structure to string                 |
|ctime         |Convert time_t value to string                 |
|gmtime        |Convert time_t to tm as UTC time               |
|localtime     |Convert time_t to tm as local time             |
|strftime      |Format time as string                          |
**Macro Constants (macros)**
|CLOCKS_PER_SEC|Clock ticks per second                         |
|NULL          |Null pointer                                   |
**Types**
|clock_t       |Clock type                                     |
|size_t        |Unsigned integral type                         |
|time_t        |Time type                                      |
|struct tm     |Time structure                                 |