time_t
From cppreference.com
                    
                                        
                    
                    
                                                            
                    |   Defined in header <time.h>
   | 
||
|   typedef /* unspecified */ time_t;  | 
||
Arithmetic type capable of representing times.
Although not defined, this is almost always a integral value holding the number of seconds since 00:00, Jan 1 1970 UTC, corresponding to POSIX time.
[edit] See also
|    returns the current time of the system as time since epoch  (function)  | |
|    converts time since epoch to calendar time expressed as local time  (function)  | |
|    converts time since epoch to calendar time expressed as Universal Coordinated Time  (function)  | |
|   C++ documentation for time_t 
 | |