cppreference.com > Standard C Date & Time > strftime strftime Syntax:
      #include <time.h>
      size_t strftime( char *str, size_t maxsize, const char *fmt, struct tm *time );
The function strftime() formats date and time information from time to a format specified by fmt, then stores the result in str (up to maxsize characters). Certain codes may be used in fmt to specify different types of time:
Code | Meaning
--- | ---
%a | abbreviated weekday name (e.g. Fri)
%A | full weekday name (e.g. Friday)
%b | abbreviated month name (e.g. Oct)
%B | full month name (e.g. October)
%c | the standard date and time string
%d | day of the month, as a number (1-31)
%H | hour, 24 hour format (0-23)
%I | hour, 12 hour format (1-12)
%j | day of the year, as a number (1-366)
%m | month as a number (1-12). Note: some versions of Microsoft Visual C++ may use values that range from 0-11.
%M | minute as a number (0-59)
%p | locale's equivalent of AM or PM
%S | second as a number (0-59)
%U | week of the year, (0-53), where week 1 has the first Sunday
%w | weekday as a decimal (0-6), where Sunday is 0
%W | week of the year, (0-53), where week 1 has the first Monday
%x | standard date string
%X | standard time string
%y | year in decimal, without the century (0-99)
%Y | year in decimal, with the century
%Z | time zone name
%% | a percent sign
The strftime() function returns the number of characters put into str, or zero if an error occurs. Related topics: gmtime localtime time