245 lines
7.8 KiB
Groff
245 lines
7.8 KiB
Groff
.\" Copyright (c) 1989, 1991 The Regents of the University of California.
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.\" All rights reserved.
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.\"
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.\" This code is derived from software contributed to Berkeley by
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.\" the American National Standards Committee X3, on Information
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.\" Processing Systems.
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.\"
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.\" Redistribution and use in source and binary forms, with or without
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.\" modification, are permitted provided that the following conditions
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.\" are met:
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.\" 1. Redistributions of source code must retain the above copyright
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.\" notice, this list of conditions and the following disclaimer.
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.\" 2. Redistributions in binary form must reproduce the above copyright
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.\" notice, this list of conditions and the following disclaimer in the
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.\" documentation and/or other materials provided with the distribution.
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.\" 3. Neither the name of the University nor the names of its contributors
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.\" may be used to endorse or promote products derived from this software
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.\" without specific prior written permission.
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.\"
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.\" THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
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.\" ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
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.\" IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
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.\" ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
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.\" FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
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.\" DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
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.\" OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
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.\" HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
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.\" LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
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.\" OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
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.\" SUCH DAMAGE.
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.\"
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.\" from: @(#)strftime.3 5.12 (Berkeley) 6/29/91
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.\" $NetBSD: strftime.3,v 1.23 2006/06/17 04:58:14 reed Exp $
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.\"
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.Dd April 14, 2004
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.Dt STRFTIME 3
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.Os
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.Sh NAME
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.Nm strftime
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.Nd format date and time
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.Sh LIBRARY
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.Lb libc
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.Sh SYNOPSIS
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.In time.h
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.Ft size_t
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.Fn strftime "char * restrict buf" "size_t maxsize" "const char * restrict format" "const struct tm * restrict timeptr"
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.Sh DESCRIPTION
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The
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.Fn strftime
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function formats the information from
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.Fa timeptr
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into the buffer
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.Fa buf
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according to the string pointed to by
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.Fa format .
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.Pp
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The
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.Fa format
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string consists of zero or more conversion specifications and
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ordinary characters.
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All ordinary characters are copied directly into the buffer.
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A conversion specification consists of a percent sign
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.Ql %
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and one other character.
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.Pp
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No more than
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.Fa maxsize
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characters will be placed into the array.
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If the total number of resulting characters, including the terminating
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null character, is not more than
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.Fa maxsize ,
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.Fn strftime
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returns the number of characters in the array, not counting the
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terminating null.
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Otherwise, zero is returned and the contents of the array are undefined.
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.Pp
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Each conversion specification is replaced by the characters as
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follows which are then copied into the buffer.
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.Bl -tag -width "xxxx"
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.It Cm \&%A
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is replaced by the locale's full weekday name.
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.It Cm %a
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is replaced by the locale's abbreviated weekday name.
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.It Cm \&%B
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is replaced by the locale's full month name.
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.It Cm \&%b No or Cm \&%h
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is replaced by the locale's abbreviated month name.
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.It Cm \&%C
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is replaced by the century (a year divided by 100 and truncated to an integer)
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as a decimal number [00,99].
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.It Cm \&%c
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is replaced by the locale's appropriate date and time representation.
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.It Cm \&%D
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is replaced by the date in the format
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.Dq Li %m/%d/%y .
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.It Cm \&%d
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is replaced by the day of the month as a decimal number [01,31].
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.It Cm \&%e
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is replaced by the day of month as a decimal number [1,31];
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single digits are preceded by a blank.
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.It Cm \&%F
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is replaced by the date in the format
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.Dq Li %Y-%m-%d
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(the ISO 8601 date format).
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.It Cm \&%G
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is replaced by the ISO 8601 year with century as a decimal number.
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.TP
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.It Cm \&%g
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is replaced by the ISO 8601 year without century as a decimal number (00-99).
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This is the year that includes the greater part of the week.
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(Monday as the first day of a week).
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See also the
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.Ql \&%V
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conversion specification.
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.TP
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.It Cm \&%H
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is replaced by the hour (24-hour clock) as a decimal number [00,23].
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.It Cm \&%I
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is replaced by the hour (12-hour clock) as a decimal number [01,12].
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.It Cm \&%j
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is replaced by the day of the year as a decimal number [001,366].
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.It Cm \&%k
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is replaced by the hour (24-hour clock) as a decimal number [0,23];
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single digits are preceded by a blank.
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.It Cm \&%l
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is replaced by the hour (12-hour clock) as a decimal number [1,12];
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single digits are preceded by a blank.
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.It Cm \&%M
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is replaced by the minute as a decimal number [00,59].
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.It Cm %m
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is replaced by the month as a decimal number [01,12].
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.It Cm %n
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is replaced by a newline.
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.It Cm %p
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is replaced by the locale's equivalent of either
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.Dq Tn AM
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or
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.Dq Tn PM .
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.It Cm \&%R
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is replaced by the time in the format
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.Dq Li %H:%M .
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.It Cm \&%r
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is replaced by the locale's representation of 12-hour clock time
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using AM/PM notation.
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.It Cm \&%S
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is replaced by the second as a decimal number [00,61].
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The range of
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seconds is (00-61) instead of (00-59) to allow for the periodic occurrence
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of leap seconds and double leap seconds.
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.It Cm %s
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is replaced by the number of seconds since the Epoch, UTC (see
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.Xr mktime 3 ) .
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.It Cm \&%T
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is replaced by the time in the format
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.Dq Li %H:%M:%S .
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.It Cm \&%t
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is replaced by a tab.
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.It Cm \&%U
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is replaced by the week number of the year (Sunday as the first day of
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the week) as a decimal number [00,53].
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.It Cm \&%u
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is replaced by the weekday (Monday as the first day of the week)
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as a decimal number [1,7].
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.It Cm \&%V
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is replaced by the week number of the year (Monday as the first day of
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the week) as a decimal number [01,53]. According to ISO 8601 the week
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containing January 1 is week 1 if it has four or more days in the new year,
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otherwise it is week 53 of the previous year, and the next week is week 1.
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The year is given by the
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.Ql \&%G
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conversion specification.
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.It Cm \&%v
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is replaced by the date in the format
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.Dq Li %e-%b-%Y .
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.It Cm \&%W
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is replaced by the week number of the year (Monday as the first day of
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the week) as a decimal number [00,53].
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.It Cm \&%w
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is replaced by the weekday (Sunday as the first day of the week)
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as a decimal number [0,6].
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.It Cm \&%X
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is replaced by the locale's appropriate time representation.
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.It Cm \&%x
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is replaced by the locale's appropriate date representation.
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.It Cm \&%Y
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is replaced by the year with century as a decimal number.
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.It Cm \&%y
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is replaced by the year without century as a decimal number [00,99].
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.It Cm \&%Z
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is replaced by the time zone name.
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.It Cm \&%z
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is replaced by the offset from ITC in the ISO 8601 format
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.Dq Li [-]hhmm .
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.It Cm %%
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is replaced by
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.Ql % .
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.El
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.Sh SEE ALSO
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.Xr date 1 ,
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.Xr printf 1 ,
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.Xr ctime 3 ,
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.Xr printf 3 ,
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.Xr strptime 3
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.Sh STANDARDS
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The
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.Fn strftime
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function
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conforms to
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.St -isoC-99 .
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The
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.Ql \&%C ,
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.Ql \&%D ,
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.Ql \&%e ,
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.Ql \&%g ,
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.Ql \&%G ,
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.Ql \&%h ,
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.Ql \&%k ,
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.Ql \&%l ,
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.Ql \&%n ,
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.Ql \&%r ,
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.Ql \&%R ,
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.Ql \&%s ,
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.Ql \&%t ,
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.Ql \&%T ,
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.Ql \&%u ,
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.Ql \&%V ,
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and
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.Ql \&%v
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conversion specifications are extensions.
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.Pp
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Use of the ISO 8601 conversions may produce non-intuitive results.
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Week 01 of a year is per definition the first week which has the Thursday
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in this year, which is equivalent to the week which contains the fourth
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day of January.
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In other words, the first week of a new year is the week which has the
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majority of its days in the new year.
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Week 01 might also contain days from the previous year and the week
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before week 01 of a year is the last week (52 or 53) of the previous
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year even if it contains days from the new year.
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A week starts with Monday (day 1) and ends with Sunday (day 7).
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For example, the first week of the year 1997 lasts from
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1996-12-30 to 1997-01-05.
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.Sh BUGS
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There is no conversion specification for the phase of the moon.
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