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.
The format string used in <code>strftime</code> traces back to at least PWB/UNIX 1.0, released in 1977. Its <code>date</code> system command includes various formatting options. In 1989, the ANSI C standard is released including <code>strftime</code> and other date and time functions.
The C date and time operations are defined in the <code><time.h></code> header file (<code><ctime></code> 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++ with the release of C++20 in <code>std::chrono</code>.
The following C source code prints the current time to the standard output stream.
The output is: