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