--- name: "strftime" section: "3" platform: "macos" package: "Libc" version: "1752.120.2" release: "macOS 26.5" platforms: ["linux", "freebsd", "macos"] url: "https://new.carta.tech/strftime" --- # strftime(3) format date and time ## NAME **strftime**, **strftime\_l** – format date and time ## LIBRARY Standard C Library (libc, -lc) ## SYNOPSIS **#include \** *size\_t*\ **strftime**(*char \*restrict s*, *size\_t maxsize*, *const char \*restrict format*, *const struct tm \*restrict timeptr*); **#include \** **#include \** *size\_t*\ **strftime\_l**(*char \*restrict s*, *size\_t maxsize*, *const char \*restrict format*, *const struct tm \*restrict timeptr*, *locale\_t loc*); ## DESCRIPTION The **strftime**() function formats the information from *timeptr* into the buffer *s*, according to the string pointed to by *format*. The *format* string consists of zero or more conversion specifications and ordinary characters. All ordinary characters are copied directly into the buffer. A conversion specification consists of a percent sign “‘%’” and one other character. No more than *maxsize* characters will be placed into the array. If the total number of resulting characters, including the terminating NUL character, is not more than *maxsize*, **strftime**() returns the number of characters in the array, not counting the terminating NUL. Otherwise, zero is returned and the buffer contents are indeterminate. Although the **strftime**() function uses the current locale, the **strftime\_l**() function may be passed a locale directly. See [xlocale(3)](/xlocale/3.md) for more information. The conversion specifications are copied to the buffer after expansion as follows:- - **%A** is replaced by national representation of the full weekday name. - **%a** is replaced by national representation of the abbreviated weekday name. - **%B** is replaced by national representation of the full month name. - **%b** is replaced by national representation of the abbreviated month name. - **%C** is replaced by (year / 100) as decimal number; single digits are preceded by a zero. - **%c** is replaced by national representation of time and date. - **%D** is equivalent to “%m/%d/%y”. - **%d** is replaced by the day of the month as a decimal number (01-31). - **%E\*** **%O\*** POSIX locale extensions. The sequences %Ec %EC %Ex %EX %Ey %EY %Od %Oe %OH %OI %Om %OM %OS %Ou %OU %OV %Ow %OW %Oy are supposed to provide alternate representations. Additionally %OB implemented to represent alternative months names (used standalone, without day mentioned). - **%e** is replaced by the day of the month as a decimal number (1-31); single digits are preceded by a blank. - **%F** is equivalent to “%Y-%m-%d”. - **%G** is replaced by a year as a decimal number with century. This year is the one that contains the greater part of the week (Monday as the first day of the week). - **%g** is replaced by the same year as in “%G”, but as a decimal number without century (00-99). - **%H** is replaced by the hour (24-hour clock) as a decimal number (00-23). - **%h** the same as **%b**. - **%I** is replaced by the hour (12-hour clock) as a decimal number (01-12). - **%j** is replaced by the day of the year as a decimal number (001-366). - **%k** is replaced by the hour (24-hour clock) as a decimal number (0-23); single digits are preceded by a blank. - **%l** is replaced by the hour (12-hour clock) as a decimal number (1-12); single digits are preceded by a blank. - **%M** is replaced by the minute as a decimal number (00-59). - **%m** is replaced by the month as a decimal number (01-12). - **%n** is replaced by a newline. - **%O\*** the same as **%E\***. - **%p** is replaced by national representation of either "ante meridiem" (a.m.) or "post meridiem" (p.m.) as appropriate. - **%R** is equivalent to “%H:%M”. - **%r** is equivalent to “%I:%M:%S %p”. - **%S** is replaced by the second as a decimal number (00-60). - **%s** is replaced by the number of seconds since the Epoch, UTC (see [mktime(3)](/mktime/3.md)). - **%T** is equivalent to “%H:%M:%S”. - **%t** is replaced by a tab. - **%U** is replaced by the week number of the year (Sunday as the first day of the week) as a decimal number (00-53). - **%u** is replaced by the weekday (Monday as the first day of the week) as a decimal number (1-7). - **%V** is replaced by the week number of the year (Monday as the first day of the week) as a decimal number (01-53). If the week containing January 1 has four or more days in the new year, then it is week 1; otherwise it is the last week of the previous year, and the next week is week 1. - **%v** is equivalent to “%e-%b-%Y”. - **%W** is replaced by the week number of the year (Monday as the first day of the week) as a decimal number (00-53). - **%w** is replaced by the weekday (Sunday as the first day of the week) as a decimal number (0-6). - **%X** is replaced by national representation of the time. - **%x** is replaced by national representation of the date. - **%Y** is replaced by the year with century as a decimal number. - **%y** is replaced by the year without century as a decimal number (00-99). - **%Z** is replaced by the time zone name. - **%z** is replaced by the time zone offset from UTC; a leading plus sign stands for east of UTC, a minus sign for west of UTC, hours and minutes follow with two digits each and no delimiter between them (common form for RFC 822 date headers). - **%+** is replaced by national representation of the date and time (the format is similar to that produced by [date(1)](/date/1.md)). - **%-\*** GNU libc extension. Do not do any padding when performing numerical outputs. - **%\_\*** GNU libc extension. Explicitly specify space for padding. - **%0\*** GNU libc extension. Explicitly specify zero for padding. - **%%** is replaced by ‘%’. ## SEE ALSO [date(1)](/date/1.md), [printf(1)](/printf/1.md), [ctime(3)](/ctime/3.md), [printf(3)](/printf/3.md), [strptime(3)](/strptime/3.md), [wcsftime(3)](/wcsftime/3.md), [xlocale(3)](/xlocale/3.md) ## STANDARDS The **strftime**() function conforms to ISO/IEC 9899:1990 (“ISO C90”) with a lot of extensions including ‘%C’, ‘%D’, ‘%E\*’, ‘%e’, ‘%G’, ‘%g’, ‘%h’, ‘%k’, ‘%l’, ‘%n’, ‘%O\*’, ‘%R’, ‘%r’, ‘%s’, ‘%T’, ‘%t’, ‘%u’, ‘%V’, ‘%z’, and ‘%+’. The peculiar week number and year in the replacements of ‘%G’, ‘%g’, and ‘%V’ are defined in ISO 8601: 1988. ## BUGS There is no conversion specification for the phase of the moon. The **strftime**() function does not correctly handle multibyte characters in the *format* argument.