path: root/man1p/date.1p

.\" Copyright (c) 2001-2003 The Open Group, All Rights Reserved 
.TH "DATE" P 2003 "IEEE/The Open Group" "POSIX Programmer's Manual"
.\" date 
.SH NAME
date \- write the date and time
.SH SYNOPSIS
.LP
\fBdate\fP \fB[\fP\fB-u\fP\fB] [\fP\fB+\fP\fIformat\fP\fB]\fP\fB
.br
.sp
\fP
.LP
\fBdate\fP \fB[\fP\fB-u\fP\fB]\fP
\fImmddhhmm\fP\fB[[\fP\fIcc\fP\fB]\fP\fIyy\fP\fB]\fP\fB\fP
\fB
.br
\fP
.SH DESCRIPTION
.LP
The \fIdate\fP utility shall write the date and time to standard output
\ or attempt
to set the system date and time.  By default, the current date and
time shall be written. If an operand beginning with \fB'+'\fP is specified,
the output format of \fIdate\fP shall be controlled
by the conversion specifications and other text in the operand.
.SH OPTIONS
.LP
The \fIdate\fP utility shall conform to the Base Definitions volume
of IEEE\ Std\ 1003.1-2001, Section 12.2, Utility Syntax Guidelines.
.LP
The following option shall be supported:
.TP 7
\fB-u\fP
Perform operations as if the \fITZ\fP environment variable was set
to the string \fB"UTC0"\fP , or its equivalent
historical value of \fB"GMT0"\fP . Otherwise, \fIdate\fP shall use
the timezone indicated by the \fITZ\fP environment variable
or the system default if that variable is unset or null.
.sp
.SH OPERANDS
.LP
The following operands shall be supported:
.TP 7
+\fIformat\fP
When the format is specified, each conversion specifier shall be replaced
in the standard output by its corresponding value.
All other characters shall be copied to the output without change.
The output shall always be terminated with a
<newline>.
.sp
.SS Conversion Specifications
.TP 7
\fB%a\fP
Locale's abbreviated weekday name.
.TP 7
\fB%A\fP
Locale's full weekday name.
.TP 7
\fB%b\fP
Locale's abbreviated month name.
.TP 7
\fB%B\fP
Locale's full month name.
.TP 7
\fB%c\fP
Locale's appropriate date and time representation.
.TP 7
\fB%C\fP
Century (a year divided by 100 and truncated to an integer) as a decimal
number [00,99].
.TP 7
\fB%d\fP
Day of the month as a decimal number [01,31].
.TP 7
\fB%D\fP
Date in the format \fImm\fP/\fIdd\fP/\fIyy\fP.
.TP 7
\fB%e\fP
Day of the month as a decimal number [1,31] in a two-digit field with
leading space character fill.
.TP 7
\fB%h\fP
A synonym for \fB%b\fP .
.TP 7
\fB%H\fP
Hour (24-hour clock) as a decimal number [00,23].
.TP 7
\fB%I\fP
Hour (12-hour clock) as a decimal number [01,12].
.TP 7
\fB%j\fP
Day of the year as a decimal number [001,366].
.TP 7
\fB%m\fP
Month as a decimal number [01,12].
.TP 7
\fB%M\fP
Minute as a decimal number [00,59].
.TP 7
\fB%n\fP
A <newline>.
.TP 7
\fB%p\fP
Locale's equivalent of either AM or PM.
.TP 7
\fB%r\fP
12-hour clock time [01,12] using the AM/PM notation; in the POSIX
locale, this shall be equivalent to \fB%I\fP : \fB%M\fP
: \fB%S\fP \fB%p\fP .
.TP 7
\fB%S\fP
Seconds as a decimal number [00,60].
.TP 7
\fB%t\fP
A <tab>.
.TP 7
\fB%T\fP
24-hour clock time [00,23] in the format \fIHH\fP:\fIMM\fP:\fISS\fP.
.TP 7
\fB%u\fP
Weekday as a decimal number [1,7] (1=Monday).
.TP 7
\fB%U\fP
Week of the year (Sunday as the first day of the week) as a decimal
number [00,53]. All days in a new year preceding the first
Sunday shall be considered to be in week 0.
.TP 7
\fB%V\fP
Week 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 shall be considered week 1;
otherwise, it shall be the last week of the previous year, and
the next week shall be week 1.
.TP 7
\fB%w\fP
Weekday as a decimal number [0,6] (0=Sunday).
.TP 7
\fB%W\fP
Week of the year (Monday as the first day of the week) as a decimal
number [00,53]. All days in a new year preceding the first
Monday shall be considered to be in week 0.
.TP 7
\fB%x\fP
Locale's appropriate date representation.
.TP 7
\fB%X\fP
Locale's appropriate time representation.
.TP 7
\fB%y\fP
Year within century [00,99].
.TP 7
\fB%Y\fP
Year with century as a decimal number.
.TP 7
\fB%Z\fP
Timezone name, or no characters if no timezone is determinable.
.TP 7
\fB%%\fP
A percent sign character.
.sp
.LP
See the Base Definitions volume of IEEE\ Std\ 1003.1-2001, Section
7.3.5, LC_TIME for the conversion specifier values in the POSIX locale.
.SS Modified Conversion Specifications
.LP
Some conversion specifiers can be modified by the \fBE\fP and \fBO\fP
modifier characters to indicate a different format
or specification as specified in the \fILC_TIME\fP locale description
(see the Base Definitions volume of
IEEE\ Std\ 1003.1-2001, Section 7.3.5, LC_TIME). If the
corresponding keyword (see \fBera\fP, \fBera_year\fP, \fBera_d_fmt\fP,
and \fBalt_digits\fP in the Base Definitions volume of
IEEE\ Std\ 1003.1-2001, Section 7.3.5, LC_TIME) is not specified or
not supported for the current locale, the unmodified conversion specifier
value shall be used.
.TP 7
\fB%Ec\fP
Locale's alternative appropriate date and time representation.
.TP 7
\fB%EC\fP
The name of the base year (period) in the locale's alternative representation.
.TP 7
\fB%Ex\fP
Locale's alternative date representation.
.TP 7
\fB%EX\fP
Locale's alternative time representation.
.TP 7
\fB%Ey\fP
Offset from \fB%EC\fP (year only) in the locale's alternative representation.
.TP 7
\fB%EY\fP
Full alternative year representation.
.TP 7
\fB%Od\fP
Day of month using the locale's alternative numeric symbols.
.TP 7
\fB%Oe\fP
Day of month using the locale's alternative numeric symbols.
.TP 7
\fB%OH\fP
Hour (24-hour clock) using the locale's alternative numeric symbols.
.TP 7
\fB%OI\fP
Hour (12-hour clock) using the locale's alternative numeric symbols.
.TP 7
\fB%Om\fP
Month using the locale's alternative numeric symbols.
.TP 7
\fB%OM\fP
Minutes using the locale's alternative numeric symbols.
.TP 7
\fB%OS\fP
Seconds using the locale's alternative numeric symbols.
.TP 7
\fB%Ou\fP
Weekday as a number in the locale's alternative representation (Monday
= 1).
.TP 7
\fB%OU\fP
Week number of the year (Sunday as the first day of the week) using
the locale's alternative numeric symbols.
.TP 7
\fB%OV\fP
Week number of the year (Monday as the first day of the week, rules
corresponding to \fB%V\fP ), using the locale's
alternative numeric symbols.
.TP 7
\fB%Ow\fP
Weekday as a number in the locale's alternative representation (Sunday
= 0).
.TP 7
\fB%OW\fP
Week number of the year (Monday as the first day of the week) using
the locale's alternative numeric symbols.
.TP 7
\fB%Oy\fP
Year (offset from \fB%C\fP ) in alternative representation.
.sp
.sp
.TP 7
\fImmddhhmm\fP\fB[[\fP\fIcc\fP\fB]\fP\fIyy\fP\fB]\fP
.sp
Attempt to set the system date and time from the value given in the
operand. This is only possible if the user has appropriate
privileges and the system permits the setting of the system date and
time. The first \fImm\fP is the month (number); \fIdd\fP is
the day (number); \fIhh\fP is the hour (number, 24-hour system); the
second \fImm\fP is the minute (number); \fIcc\fP is the
century and is the first two digits of the year (this is optional);
\fIyy\fP is the last two digits of the year and is optional.
If century is not specified, then values in the range [69,99] shall
refer to years 1969 to 1999 inclusive, and values in the range
[00,68] shall refer to years 2000 to 2068 inclusive. The current year
is the default if \fIyy\fP is omitted.   
.TP 7
\fBNote:\fP
.RS
It is expected that in a future version of IEEE\ Std\ 1003.1-2001
the default century inferred from a 2-digit year will
change. (This would apply to all commands accepting a 2-digit year
as input.)
.RE
.sp
.sp
.SH STDIN
.LP
Not used.
.SH INPUT FILES
.LP
None.
.SH ENVIRONMENT VARIABLES
.LP
The following environment variables shall affect the execution of
\fIdate\fP:
.TP 7
\fILANG\fP
Provide a default value for the internationalization variables that
are unset or null. (See the Base Definitions volume of
IEEE\ Std\ 1003.1-2001, Section 8.2, Internationalization Variables
for
the precedence of internationalization variables used to determine
the values of locale categories.)
.TP 7
\fILC_ALL\fP
If set to a non-empty string value, override the values of all the
other internationalization variables.
.TP 7
\fILC_CTYPE\fP
Determine the locale for the interpretation of sequences of bytes
of text data as characters (for example, single-byte as
opposed to multi-byte characters in arguments).
.TP 7
\fILC_MESSAGES\fP
Determine the locale that should be used to affect the format and
contents of diagnostic messages written to standard
error.
.TP 7
\fILC_TIME\fP
Determine the format and contents of date and time strings written
by \fIdate\fP.
.TP 7
\fINLSPATH\fP
Determine the location of message catalogs for the processing of \fILC_MESSAGES
\&.\fP 
.TP 7
\fITZ\fP
Determine the timezone in which the time and date are written, unless
the \fB-u\fP option is specified. If the \fITZ\fP
variable is unset or null and \fB-u\fP is not specified, an unspecified
system default timezone is used.
.sp
.SH ASYNCHRONOUS EVENTS
.LP
Default.
.SH STDOUT
.LP
When no formatting operand is specified, the output in the POSIX locale
shall be equivalent to specifying:
.sp
.RS
.nf

\fBdate "+%a %b %e %H:%M:%S %Z %Y"
\fP
.fi
.RE
.SH STDERR
.LP
The standard error shall be used only for diagnostic messages.
.SH OUTPUT FILES
.LP
None.
.SH EXTENDED DESCRIPTION
.LP
None.
.SH EXIT STATUS
.LP
The following exit values shall be returned:
.TP 7
\ 0
The date was written successfully.
.TP 7
>0
An error occurred.
.sp
.SH CONSEQUENCES OF ERRORS
.LP
Default.
.LP
\fIThe following sections are informative.\fP
.SH APPLICATION USAGE
.LP
Conversion specifiers are of unspecified format when not in the POSIX
locale. Some of them can contain <newline>s in some
locales, so it may be difficult to use the format shown in standard
output for parsing the output of \fIdate\fP in those
locales.
.LP
The range of values for \fB%S\fP extends from 0 to 60 seconds to accommodate
the occasional leap second.
.LP
Although certain of the conversion specifiers in the POSIX locale
(such as the name of the month) are shown with initial capital
letters, this need not be the case in other locales. Programs using
these fields may need to adjust the capitalization if the
output is going to be used at the beginning of a sentence.
.LP
The date string formatting capabilities are intended for use in Gregorian-style
calendars, possibly with a different starting
year (or years). The \fB%x\fP and \fB%c\fP conversion specifications,
however, are intended for local representation; these
may be based on a different, non-Gregorian calendar.
.LP
The \fB%C\fP conversion specification was introduced to allow a fallback
for the \fB%EC\fP (alternative year format base
year); it can be viewed as the base of the current subdivision in
the Gregorian calendar. The century number is calculated as the
year divided by 100 and truncated to an integer; it should not be
confused with the use of ordinal numbers for centuries (for
example, "twenty-first century".) Both the \fB%Ey\fP and \fB%y\fP
can then be viewed as the offset from \fB%EC\fP and
\fB%C\fP , respectively.
.LP
The \fBE\fP and \fBO\fP modifiers modify the traditional conversion
specifiers, so that they can always be used, even if
the implementation (or the current locale) does not support the modifier.
.LP
The \fBE\fP modifier supports alternative date formats, such as the
Japanese Emperor's Era, as long as these are based on the
Gregorian calendar system. Extending the \fBE\fP modifiers to other
date elements may provide an implementation-defined
extension capable of supporting other calendar systems, especially
in combination with the \fBO\fP modifier.
.LP
The \fBO\fP modifier supports time and date formats using the locale's
alternative numerical symbols, such as Kanji or Hindi
digits or ordinal number representation.
.LP
Non-European locales, whether they use Latin digits in computational
items or not, often have local forms of the digits for use
in date formats. This is not totally unknown even in Europe; a variant
of dates uses Roman numerals for the months: the third day
of September 1991 would be written as 3.IX.1991. In Japan, Kanji digits
are regularly used for dates; in Arabic-speaking countries,
Hindi digits are used. The \fB%d\fP , \fB%e\fP , \fB%H\fP , \fB%I\fP
, \fB%m\fP , \fB%S\fP , \fB%U\fP ,
\fB%w\fP , \fB%W\fP , and \fB%y\fP conversion specifications always
return the date and time field in Latin digits (that
is, 0 to 9). The \fB%O\fP modifier was introduced to support the use
for display purposes of non-Latin digits. In the
\fILC_TIME\fP category in \fIlocaledef\fP, the optional \fBalt_digits\fP
keyword is
intended for this purpose. As an example, assume the following (partial)
\fIlocaledef\fP
source:
.sp
.RS
.nf

\fBalt_digits  "";"I";"II";"III";"IV";"V";"VI";"VII";"VIII" \\
            "IX";"X";"XI";"XII"
d_fmt       "%e.%Om.%Y"
\fP
.fi
.RE
.LP
With the above date, the command:
.sp
.RS
.nf

\fBdate "+%x"
\fP
.fi
.RE
.LP
would yield 3.IX.1991. With the same \fBd_fmt\fP, but without the
\fBalt_digits\fP, the command would yield 3.9.1991.
.SH EXAMPLES
.IP " 1." 4
The following are input/output examples of \fIdate\fP used at arbitrary
times in the POSIX locale:
.sp
.RS
.nf

\fB$\fP \fBdate
\fP\fBTue Jun 26 09:58:10 PDT 1990
.sp

$\fP \fBdate "+DATE: %m/%d/%y%nTIME: %H:%M:%S"
\fP\fBDATE: 11/02/91
TIME: 13:36:16
.sp

$\fP \fBdate "+TIME: %r"
\fP\fBTIME: 01:36:32 PM\fP
.fi
.RE
.LP
.IP " 2." 4
Examples for Denmark, where the default date and time format is \fB%a\fP
\fB%d\fP \fB%b\fP \fB%Y\fP \fB%T\fP
\fB%Z\fP :
.sp
.RS
.nf

\fB$\fP \fBLANG=da_DK.iso_8859-1 date
\fP\fBons 02 okt 1991 15:03:32 CET
.sp

$\fP \fBLANG=da_DK.iso_8859-1 \\
    date "+DATO: %A den %e. %B %Y%nKLOKKEN: %H:%M:%S"
\fP\fBDATO: onsdag den 2. oktober 1991
KLOKKEN: 15:03:56\fP
.fi
.RE
.LP
.IP " 3." 4
Examples for Germany, where the default date and time format is \fB%a\fP
\fB%d\fP . \fB%h\fP . \fB%Y\fP ,
\fB%T\fP \fB%Z\fP :
.sp
.RS
.nf

\fB$\fP \fBLANG=De_DE.88591 date
\fP\fBMi 02.Okt.1991, 15:01:21 MEZ
.sp

$\fP \fBLANG=De_DE.88591 date "+DATUM: %A, %d. %B %Y%nZEIT: %H:%M:%S"
\fP\fBDATUM: Mittwoch, 02. Oktober 1991
ZEIT: 15:02:02\fP
.fi
.RE
.LP
.IP " 4." 4
Examples for France, where the default date and time format is \fB%a\fP
\fB%d\fP \fB%h\fP \fB%Y\fP \fB%Z\fP
\fB%T\fP :
.sp
.RS
.nf

\fB$\fP \fBLANG=Fr_FR.88591 date
\fP\fBMer 02 oct 1991 MET 15:03:32
.sp

$\fP \fBLANG=Fr_FR.88591 date "+JOUR: %A %d %B %Y%nHEURE: %H:%M:%S"
\fP\fBJOUR: Mercredi 02 octobre 1991
HEURE: 15:03:56\fP
.fi
.RE
.LP
.SH RATIONALE
.LP
Some of the new options for formatting are from the ISO\ C standard.
The \fB-u\fP option was introduced to allow portable
access to Coordinated Universal Time (UTC). The string \fB"GMT0"\fP
is allowed as an equivalent \fITZ\fP value to be compatible
with all of the systems using the BSD implementation, where this option
originated.
.LP
The \fB%e\fP format conversion specification (adopted from System
V) was added because the ISO\ C standard conversion
specifications did not provide any way to produce the historical default
\fIdate\fP output during the first nine days of any
month.
.LP
There are two varieties of day and week numbering supported (in addition
to any others created with the locale-dependent
\fB%E\fP and \fB%O\fP modifier characters):
.IP " *" 3
The historical variety in which Sunday is the first day of the week
and the weekdays preceding the first Sunday of the year are
considered week 0. These are represented by \fB%w\fP and \fB%U\fP
\&. A variant of this is \fB%W\fP , using Monday as the
first day of the week, but still referring to week 0. This view of
the calendar was retained because so many historical
applications depend on it and the ISO\ C standard \fIstrftime\fP()
function, on which
many \fIdate\fP implementations are based, was defined in this way.
.LP
.IP " *" 3
The international standard, based on the ISO\ 8601:2000 standard where
Monday is the first weekday and the algorithm for the
first week number is more complex: If the week (Monday to Sunday)
containing January 1 has four or more days in the new year, then
it is week 1; otherwise, it is week 53 of the previous year, and the
next week is week 1. These are represented by the new
conversion specifications \fB%u\fP and \fB%V\fP , added as a result
of international comments.
.LP
.SH FUTURE DIRECTIONS
.LP
None.
.SH SEE ALSO
.LP
The System Interfaces volume of IEEE\ Std\ 1003.1-2001, \fIprintf\fP(),
\fIstrftime\fP()
.SH COPYRIGHT
Portions of this text are reprinted and reproduced in electronic form
from IEEE Std 1003.1, 2003 Edition, Standard for Information Technology
-- Portable Operating System Interface (POSIX), The Open Group Base
Specifications Issue 6, Copyright (C) 2001-2003 by the Institute of
Electrical and Electronics Engineers, Inc and The Open Group. In the
event of any discrepancy between this version and the original IEEE and
The Open Group Standard, the original IEEE and The Open Group Standard
is the referee document. The original Standard can be obtained online at
http://www.opengroup.org/unix/online.html .