strftime, cftime, ascftime - convert date and time to string
size_t strftime(char *s, size_t maxsize, const char *format,
const struct tm *timeptr);
int cftime(char *s, char *format, const time_t *clock);
int ascftime(char *s, const char *format, const struct tm
The strftime(), ascftime(), and cftime() functions place
bytes into the array pointed to by s as controlled by the
string pointed to by format. The format string consists of
zero or more conversion specifications and ordinary charac-
ters. A conversion specification consists of a '%' (per-
cent) character and one or two terminating conversion char-
acters that determine the conversion specification's
behavior. All ordinary characters (including the terminat-
ing null byte) are copied unchanged into the array pointed
to by s. If copying takes place between objects that over-
lap, the behavior is undefined. For strftime (), no more
than maxsize bytes are placed into the array.
If format is (char *)0, then the locale's default format is
used. For strftime() the default format is the same as %c;
for cftime() and ascftime() the default format is the same
as %C. cftime() and ascftime() first try to use the value of
the environment variable CFTIME, and if that is undefined or
empty, the default format is used.
Each conversion specification is replaced by appropriate
characters as described in the following list. The appropri-
ate characters are determined by the LC_TIME category of the
program's locale and by the values contained in the struc-
ture pointed to by timeptr for strftime() and ascftime(),
and by the time represented by clock for cftime().
%% Same as %.
%a Locale's abbreviated weekday name.
%A Locale's full weekday name.
%b Locale's abbreviated month name.
%B Locale's full month name.
%c Locale's appropriate date and time representation.
%C Locale's date and time representation as produced by
%C Century number (the year divided by 100 and truncated
to an integer as a decimal number [1,99]); single
digits are preceded by 0; see standards(5).
%d Day of month [1,31]; single digits are preceded by 0.
%D Date as %m/%d/%y.
%e Day of month [1,31]; single digits are preceded by a
%g Week-based year within century [00,99].
%G Week-based year, including the century [0000,9999].
%h Locale's abbreviated month name.
%H Hour (24-hour clock) [0,23]; single digits are pre-
ceded by 0.
%I Hour (12-hour clock) [1,12]; single digits are pre-
ceded by 0.
%j Day number of year [1,366]; single digits are preceded
%k Hour (24-hour clock) [0,23]; single digits are pre-
ceded by a blank.
%l Hour (12-hour clock) [1,12]; single digits are pre-
ceded by a blank.
%m Month number [1,12]; single digits are preceded by 0.
%M Minute [00,59]; leading 0 is permitted but not
%n Insert a NEWLINE.
%p Locale's equivalent of either a.m. or p.m.
%r Appropriate time representation in 12-hour clock for-
mat with %p.
%R Time as %H:%M.
%S Seconds [00,61]; the range of values is [00,61] rather
than [00,59] to allow for the occasional leap second
and even more occasional double leap second.
%t Insert a TAB.
%T Time as %H:%M:%S.
%u Weekday as a decimal number [1,7], with 1 representing
Monday. See NOTES below.
%U Week number of year as a decimal number [00,53], with
Sunday as the first day of week 1.
%V The ISO 8601 week number as a decimal number [01,53].
In the ISO 8601 week-based system, weeks begin on a
Monday and week 1 of the year is the week that
includes both January 4th and the first Thursday of
the year. If the first Monday of January is the 2nd,
3rd, or 4th, the preceding days are part of the last
week of the preceding year. See NOTES below.
%w Weekday as a decimal number [0,6], with 0 representing
%W Week number of year as a decimal number [00,53], with
Monday as the first day of week 1.
%x Locale's appropriate date representation.
%X Locale's appropriate time representation.
%y Year within century [00,99].
%Y Year, including the century (for example 1993).
%Z Time zone name or abbreviation, or no bytes if no time
zone information exists.
If a conversion specification does not correspond to any of
the above or to any of the modified conversion specifica-
tions listed below, the behavior is undefined and 0 is
The difference between %U and %W (and also between modified
conversion specifications %OU and %OW) lies in which day is
counted as the first of the week. Week number 1 is the first
week in January starting with a Sunday for %U or a Monday
for %W. Week number 0 contains those days before the first
Sunday or Monday in January for %U and %W, respectively.
Modified Conversion Specifications
Some conversion specifications can be modified by the E and
O modifiers to indicate that an alternate format or specifi-
cation should be used rather than the one normally used by
the unmodified conversion specification. If the alternate
format or specification does not exist in the current
locale, the behavior will be as if the unmodified specifica-
tion were used.
%Ec Locale's alternate appropriate date and time represen-
%EC Name of the base year (period) in the locale's alter-
%Eg Offset from %EC of the week-based year in the locale's
%EG Full alternative representation of the week-based
%Ex Locale's alternate date representation.
%EX Locale's alternate time representation.
%Ey Offset from %EC (year only) in the locale's alternate
%EY Full alternate year representation.
%Od Day of the month using the locale's alternate numeric
%Oe Same as %Od.
%Og Week-based year (offset from %C) in the locale's
alternate representation and using the locale's alter-
nate numeric symbols.
%OH Hour (24-hour clock) using the locale's alternate
%OI Hour (12-hour clock) using the locale's alternate
%Om Month using the locale's alternate numeric symbols.
%OM Minutes using the locale's alternate numeric symbols.
%OS Seconds using the locale's alternate numeric symbols.
%Ou Weekday as a number in the locale's alternate numeric
%OU Week number of the year (Sunday as the first day of
the week) using the locale's alternate numeric sym-
%Ow Number of the weekday (Sunday=0) using the locale's
alternate numeric symbols.
%OW Week number of the year (Monday as the first day of
the week) using the locale's alternate numeric sym-
%Oy Year (offset from %C) in the locale's alternate
representation and using the locale's alternate
Selecting the Output Language
By default, the output of strftime(), cftime(), and ascf-
time() appear in U.S. English. The user can request that the
output of strftime(), cftime(), or ascftime() be in a
specific language by setting the LC_TIME category using set-
Local time zone information is used as though tzset(3C) were
The strftime(), cftime(), and ascftime() functions return
the number of characters placed into the array pointed to by
s, not including the terminating null character. If the
total number of resulting characters including the terminat-
ing null character is more than maxsize, strftime() returns
0 and the contents of the array are indeterminate.
Example 1: An example of the strftime() function.
The following example illustrates the use of strftime() for
the POSIX locale. It shows what the string in str would look
like if the structure pointed to by tmptr contains the
values corresponding to Thursday, August 28, 1986 at
strftime (str, strsize, "%A %b %d %j", tmptr)
This results in str containing "Thursday Aug 28 240".
See attributes(5) for descriptions of the following attri-
| ATTRIBUTE TYPE | ATTRIBUTE VALUE |
| MT-Level | MT-Safe |
| CSI | Enabled |
date(1), ctime(3C), mktime(3C), setlocale(3C), strptime(3C),
tzset(3C), TIMEZONE(4), zoneinfo(4), attributes(5),
The conversion specification for %V was changed in the
Solaris 7 release. This change was based on the public
review draft of the ISO C9x standard at that time. Previ-
ously, the specification stated that if the week containing
1 January had fewer than four days in the new year, it
became week 53 of the previous year. The ISO C9x standard
committee subsequently recognized that that specification
had been incorrect.
The conversion specifications for %g, %G, %Eg, %EG, and %Og
were added in the Solaris 7 release. This change was based
on the public review draft of the ISO C9x standard at that
time. These specifications are evolving. If the ISO C9x
standard is finalized with a different conclusion, these
specifications will change to conform to the ISO C9x stan-
The conversion specification for %u was changed in the
Solaris 8 release. This change was based on the XPG4 specif-
If using the %Z specifier and zoneinfo timezones and if the
input date is outside the range 20:45:52 UTC, December 13,
1901 to 03:14:07 UTC, January 19, 2038, the timezone name
may not be correct.
Man(1) output converted with