The C date and time functions are a group of functions in the standard library of the C programming language implementing date and time manipulation operations. They provide support for time acquisition, conversion between date formats, and formatted output to strings. Overview of functions The C date and time operations are defined in the time.h header file (ctime header in C++). The and related types were originally proposed by Markus Kuhn to provide a variety of time bases, but only was accepted. The functionalities were, however, added to C++ in 2020 in std::chrono. Example The following C source code prints the current time to the standard output stream. #include <time.h> #include <stdlib.h> #include <stdio.h> int main(void) { time_t current_time; char* c_time_string; /* Obtain current time. */ current_time = time(NULL); if (current_time == ((time_t)-1)) { (void) fprintf(stderr, "Failure to obtain the current time.\n"); exit(EXIT_FAILURE); } /* Convert to local time format. */ c_time_string = ctime(&current_time); if (c_time_string == NULL) { (void) fprintf(stderr, "Failure to convert the current time.\n"); exit(EXIT_FAILURE); } /* Print to stdout. ctime() has already added a terminating newline character. */ (void) printf("Current time is %s", c_time_string); exit(EXIT_SUCCESS); } The output is: Current time is Thu Sep 15 21:18:23 2016 See also Unix time Year 2038 problem References External links C standard library Time