strftime

From cppreference.com
Defined in header <time.h>
size_t strftime ( char * str, size_t count,
const char * format, const struct tm * tp ) ;
(until C99)
size_t strftime ( char * restrict str, size_t count,
const char * restrict format, const struct tm * restrict tp ) ;
(since C99)

Converts the date and time information from a given calendar time tp to a null-terminated multibyte character string str according to format string format . Up to count bytes are written.

Parameters

str - pointer to the first element of the char array for output
count - maximum number of bytes to write
format - pointer to a null-terminated multibyte character string specifying the format of conversion
tp - pointer to a struct tm object specifying the time to format

Format string

The format string consists of zero or more conversion specifiers and ordinary characters (except % ). All ordinary characters, including the terminating null character, are copied to the output string without modification. Each conversion specification begins with % character, optionally followed by E or O modifier (ignored if unsupported by the locale), followed by the character that determines the behavior of the specifier. The following format specifiers are available:

Conversion
specifier
Explanation Used fields
% writes literal % . The full conversion specification must be %% .
n
(C99)
writes newline character
t
(C99)
writes horizontal tab character
Year
Y writes year as a decimal number, e.g. 2017 tm_year
EY
(C99)
writes year in the alternative representation, e.g.平成23年 (year Heisei 23) instead of 2011年 (year 2011) in ja_JP locale tm_year
y writes last 2 digits of year as a decimal number (range [00,99] ) tm_year
Oy
(C99)
writes last 2 digits of year using the alternative numeric system, e.g. 十一 instead of 11 in ja_JP locale tm_year
Ey
(C99)
writes year as offset from locale's alternative calendar period %EC (locale-dependent) tm_year
C
(C99)
writes first 2 digits of year as a decimal number (range [00,99] ) tm_year
EC
(C99)
writes name of the base year (period) in the locale's alternative representation, e.g. 平成 (Heisei era) in ja_JP tm_year
G
(C99)
writes ISO 8601 week-based year , i.e. the year that contains the specified week.

In ISO 8601 weeks begin with Monday and the first week of the year must satisfy the following requirements:

  • Includes January 4
  • Includes first Thursday of the year
tm_year , tm_wday , tm_yday
g
(C99)
writes last 2 digits of ISO 8601 week-based year , i.e. the year that contains the specified week (range [00,99] ).

In ISO 8601 weeks begin with Monday and the first week of the year must satisfy the following requirements:

  • Includes January 4
  • Includes first Thursday of the year
tm_year , tm_wday , tm_yday
Month
b writes abbreviated month name, e.g. Oct (locale dependent) tm_mon
Ob
(C23)
writes abbreviated month name in the locale's alternative representation tm_mon
h
(C99)
synonym of b tm_mon
B writes full month name, e.g. October (locale dependent) tm_mon
OB
(C23)
writes appropriate full month name in the locale's alternative representation tm_mon
m writes month as a decimal number (range [01,12] ) tm_mon
Om
(C99)
writes month using the alternative numeric system, e.g. 十二 instead of 12 in ja_JP locale tm_mon
Week
U writes week of the year as a decimal number (Sunday is the first day of the week) (range [00,53] ) tm_year , tm_wday , tm_yday
OU
(C99)
writes week of the year , as by %U , using the alternative numeric system, e.g. 五十二 instead of 52 in ja_JP locale tm_year , tm_wday , tm_yday
W writes week of the year as a decimal number (Monday is the first day of the week) (range [00,53] ) tm_year , tm_wday , tm_yday
OW
(C99)
writes week of the year , as by %W , using the alternative numeric system, e.g. 五十二 instead of 52 in ja_JP locale tm_year , tm_wday , tm_yday
V
(C99)
writes ISO 8601 week of the year (range [01,53] ).

In ISO 8601 weeks begin with Monday and the first week of the year must satisfy the following requirements:

  • Includes January 4
  • Includes first Thursday of the year
tm_year , tm_wday , tm_yday
OV
(C99)
writes week of the year , as by %V , using the alternative numeric system, e.g. 五十二 instead of 52 in ja_JP locale tm_year , tm_wday , tm_yday
Day of the year/month
j writes day of the year as a decimal number (range [001,366] ) tm_yday
d writes day of the month as a decimal number (range [01,31] ) tm_mday
Od
(C99)
writes zero-based day of the month using the alternative numeric system, e.g. 二十七 instead of 27 in ja_JP locale

Single character is preceded by a space.

tm_mday
e
(C99)
writes day of the month as a decimal number (range [1,31] ).

Single digit is preceded by a space.

tm_mday
Oe
(C99)
writes one-based day of the month using the alternative numeric system, e.g. 二十七 instead of 27 in ja_JP locale

Single character is preceded by a space.

tm_mday
Day of the week
a writes abbreviated weekday name, e.g. Fri (locale dependent) tm_wday
A writes full weekday name, e.g. Friday (locale dependent) tm_wday
w writes weekday as a decimal number, where Sunday is 0 (range [0-6] ) tm_wday
Ow
(C99)
writes weekday , where Sunday is 0 , using the alternative numeric system, e.g. 二 instead of 2 in ja_JP locale tm_wday
u
(C99)
writes weekday as a decimal number, where Monday is 1 (ISO 8601 format) (range [1-7] ) tm_wday
Ou
(C99)
writes weekday , where Monday is 1 , using the alternative numeric system, e.g. 二 instead of 2 in ja_JP locale tm_wday
Hour, minute, second
H writes hour as a decimal number, 24 hour clock (range [00-23] ) tm_hour
OH
(C99)
writes hour from 24-hour clock using the alternative numeric system, e.g. 十八 instead of 18 in ja_JP locale tm_hour
I writes hour as a decimal number, 12 hour clock (range [01,12] ) tm_hour
OI
(C99)
writes hour from 12-hour clock using the alternative numeric system, e.g. 六 instead of 06 in ja_JP locale tm_hour
M writes minute as a decimal number (range [00,59] ) tm_min
OM
(C99)
writes minute using the alternative numeric system, e.g. 二十五 instead of 25 in ja_JP locale tm_min
S writes second as a decimal number (range [00,60] ) tm_sec
OS
(C99)
writes second using the alternative numeric system, e.g. 二十四 instead of 24 in ja_JP locale tm_sec
Other
c writes standard date and time string , e.g. Sun Oct 17 04:41:13 2010 (locale dependent) all
Ec
(C99)
writes alternative date and time string , e.g. using 平成23年 (year Heisei 23) instead of 2011年 (year 2011) in ja_JP locale all
x writes localized date representation (locale dependent) all
Ex
(C99)
writes alternative date representation , e.g. using 平成23年 (year Heisei 23) instead of 2011年 (year 2011) in ja_JP locale all
X writes localized time representation , e.g. 18:40:20 or 6:40:20 PM (locale dependent) all
EX
(C99)
writes alternative time representation (locale dependent) all
D
(C99)
equivalent to "%m/%d/%y" tm_mon , tm_mday , tm_year
F
(C99)
equivalent to "%Y-%m-%d" (the ISO 8601 date format) tm_mon , tm_mday , tm_year
r
(C99)
writes localized 12-hour clock time (locale dependent) tm_hour , tm_min , tm_sec
R
(C99)
equivalent to "%H:%M" tm_hour , tm_min
T
(C99)
equivalent to "%H:%M:%S" (the ISO 8601 time format) tm_hour , tm_min , tm_sec
p writes localized a.m. or p.m. (locale dependent) tm_hour
z
(C99)
writes offset from UTC in the ISO 8601 format (e.g. -0430 ), or no characters if the time zone information is not available tm_isdst
Z writes locale-dependent time zone name or abbreviation , or no characters if the time zone information is not available tm_isdst

Return value

The number of bytes written into the character array pointed to by str not including the terminating ' \0 ' on success. If count was reached before the entire string could be stored, 0 is returned and the contents are indeterminate.

Example

#include <locale.h>
#include <stdio.h>
#include <time.h>
 
int main(void)
{
    char buff[70];
    struct tm my_time = { .tm_year=112, // = year 2012
                          .tm_mon=9,    // = 10th month
                          .tm_mday=9,   // = 9th day
                          .tm_hour=8,   // = 8 hours
                          .tm_min=10,   // = 10 minutes
                          .tm_sec=20    // = 20 secs
    };
 
    if (strftime(buff, sizeof buff, "%A %c", &my_time))
        puts(buff);
    else
        puts("strftime failed");
 
    setlocale(LC_TIME, "el_GR.utf8");
 
    if (strftime(buff, sizeof buff, "%A %c", &my_time))
        puts(buff);
    else
        puts("strftime failed");
}

Possible output:

Sunday Sun Oct  9 08:10:20 2012
Κυριακή Κυρ 09 Οκτ 2012 08:10:20 πμ EST

References

  • C23 standard (ISO/IEC 9899:2024):
  • 7.27.3.5 The strftime function (p: TBD)
  • C17 standard (ISO/IEC 9899:2018):
  • 7.27.3.5 The strftime function (p: 288-291)
  • C11 standard (ISO/IEC 9899:2011):
  • 7.27.3.5 The strftime function (p: 394-397)
  • C99 standard (ISO/IEC 9899:1999):
  • 7.23.3.5 The strftime function (p: 343-347)
  • C89/C90 standard (ISO/IEC 9899:1990):
  • 4.12.3.5 The strftime function

See also

(deprecated in C23) (C11)
converts a tm object to a textual representation
(function)
(deprecated in C23) (C11)
converts a time_t object to a textual representation
(function)
converts a tm object to custom wide string textual representation
(function)
C++ documentation for strftime