C date and time functions
| C Standard Library |
|---|
|
C date and time functions refer to a group of functions in the standard library of the C programming language implementing date and time manipulation operations.[1] They provide support for time acquisition, conversion between date formats and formatted output to strings.
Contents |
Overview of functions
The C date and time operations are defined in the time.h header file (ctime header in C++).
| Identifier | Description | |
|---|---|---|
| Time manipulation |
difftime |
computes the difference between times |
time |
returns the current time of the system as time since the epoch (which is usually the Unix epoch) | |
clock |
returns a processor tick count associated with the process | |
| Format conversions |
asctime |
converts a tm object to a textual representation |
ctime |
converts a tm object to a textual representation |
|
strftime |
converts a tm object to custom textual representation |
|
wcsftime |
converts a tm object to custom wide string textual representation |
|
gmtime |
converts time since the epoch to calendar time expressed as Universal Coordinated Time[2] | |
localtime |
converts time since the epoch to calendar time expressed as local time | |
mktime |
converts calendar time to time since the epoch | |
| Constants | CLOCKS_PER_SEC |
number of processor clock ticks per second |
| Types | tm |
calendar time type |
time_t |
time since the epoch type | |
clock_t |
process running time type |
Example
The following C source code snippet prints the current time to the standard output stream.
#include <stdio.h> #include <time.h> int main() { /* Obtain current time as seconds elapsed since the Epoch. */ time_t clock = time(NULL); /* Convert to local time format and print to stdout. */ printf("Current time is %s", ctime(&clock)); return 0; }
The output is:
Current time is Sat Dec 31 11:20:45 2011
