DATE(1) General Commands Manual DATE(1)

date — write the date and time

date [−u] [+format]

The date utility shall write the date and time to standard output. By default, the current date and time shall be written. If an operand beginning with + is specified, the output format of date shall be controlled by the field descriptors and other text in the operand.

The date utility shall conform to the utility argument syntax guidelines described in 2.10.2. The following option shall be supported by the implementation:

Perform operations as if the TZ environment variable was set to the string , or its equivalent historical value of GMT0. Otherwise, date shall use the time zone indicated by the TZ environment variable or the system default if that variable is not set.

When the format is specified, each field descriptor 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 be always terminated with a <newline> character. Field Descriptors %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 Century (a year divided by 100 and truncated to an integer) as a decimal number (00-99). %d Day of the month as a decimal number (01-31). %D Date in the format mm/dd/yy. %e Day of the month as a decimal number (1-31 in a two-digit field with leading <space> fill). %h A synonym for %b.

%H Hour (24-hour clock) as a decimal number (00-23). %I Hour (12-hour clock) as a decimal number (01-12). %j Day of the year as a decimal number (001-366). %m Month as a decimal number (01-12). %M Minute as a decimal number (00-59). %n A <newline> character. %p Locale’s equivalent of either AM or PM. %r 12-Hour clock time (01-12) using the AM/PM notation; in the POSIX Locale, this shall be equivalent to "%I:%M:%S %p". %S Seconds as a decimal number (00-61). %t A <tab> character. %T 24-Hour clock time (00-23) in the format HH:MM:SS . %U Week number of the year (Sunday as the first day of the week) as a decimal number (00-53). %w Weekday as a decimal number [0 (Sunday)-6]. %W Week number of the year (Monday as the first day of the week) as a decimal number (00-53). %x Locale’s appropriate date representation. %X Locale’s appropriate time representation. %y Year (offset from %C) as a decimal number (00-99). %Y Year with century as a decimal number. %Z Time-zone name, or no characters if no time zone is determinable. %% A <percent-sign> character. See the LC_TIME description in 2.5.2.5 for the field descriptor values in the POSIX Locale.

Modified Field Descriptors

Some field descriptors can be modified by the E and O modifier characters to indicate a different format or specification as specified in the LC_TIME locale description (see 2.5.2.5). If the corresponding keyword (see era, era_year, era_d_fmt, and alt_digits in 2.5.2.5) is not specified or not supported for the current locale, the unmodified field descriptor value shall be used. %Ec Locale’s alternate appropriate date and time representation. %EC The name of the base year (period) in the locale’s alternate representation. %Ex Locale’s alternate date representation. %Ey Offset from %EC (year only) in the locale’s alternate representation. %EY Full alternate year representation. %Od Day of month using the locale’s alternate numeric symbols. %Oe Day of month using the locale’s alternate numeric symbols. %OH Hour (24-hour clock) using the locale’s alternate numeric symbols.

%OI Hour (12-hour clock) using the locale’s alternate numeric symbols. %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 Week number of the year (Sunday as the first day of the week) using the locale’s alternate numeric symbols. %Ow Weekday as number in the locale’s alternate representation (Sunday = 0). %OW Week number of the year (Monday as the first day of the week) using the locale’s alternate numeric symbols. %Oy Year (offset from %C) in alternate representation.

None.

None.

The following environment variables shall affect the execution of date:

This variable shall determine the locale to use for the locale categories when both LC_ALL and the corresponding environment variable (beginning with LC_ ) do not specify a locale. See 2.6.

This variable shall determine the locale to be used to override any values for locale categories specified by the settings of LANG or any environment variables beginning with LC_.

This variable shall determine the locale for the interpretation of sequences of bytes of text data as characters (e.g., single- versus multibyte characters in arguments).

This variable shall determine the language in which messages should be written.

This variable shall determine the format and contents of date and time strings written by date.

This variable shall specify the time zone in which the time and date are written, unless the −u option is specified. If the TZ variable is not set and the −u is not specified, an unspecified system default time zone is used.

Default.

When no formatting operand is specified, the output in the POSIX Locale shall be equivalent to specifying date "+%a %b %e %H:%M:%S %Z %Y"

Used only for diagnostic messages.

None.

None.

The date utility shall exit with one of the following values:

The date was written successfully.

An error occurred.

Default.

The option for setting the date and time was not included. It is normally a system administration option, which is outside the scope of POSIX. 2. The following are input/output examples of date used at arbitrary times in the POSIX Locale: $ date Tue Jun 26 09:58:10 1990 $ date "+ DATE: %m/%d/%y%nTIME: %H:%M:%S" DATE: 11/21/87 TIME: 13:36:16

$ date "+ TIME: %r" TIME: 01:36:32 PM

Field descriptors 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 date in those locales. The range of values for %S extends from 0 to 61 seconds to accommodate the occasional leap second or double leap second. Although certain of the field descriptors 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. The date string formatting capabilities are intended for use in Gregorian style calendars, possibly with a different starting year (or years). The %x and %c field descriptors, however, are intended for ‘‘local representation’’; these may be based on a different, non-Gregorian calendar. The %C field descriptor was introduced to allow a fallback for the %EC (alternate year format base year); it can be viewed as the base of the current subdivision in the Gregorian calendar. A century is not calculated as an ordinal number; this standard was approved in century 19, not the twentieth (let’s hope). Both the %Ey and %y can then be viewed as the offset from %EC and %C, respectively. The E and O modifiers modify the traditional field descriptors, so that they can always be used, even if the implementation (or the current locale) does not support the modifier. The E modifier supports alternate date formats, such as the Japanese Emperor’s Era, as long as these are based on the Gregorian calendar system. Extending the E modifiers to other date elements may provide an implementation-specific

extension capable of supporting other calendar systems, especially in combination with the O modifier. The O modifier supports time and date formats using the locale’s alternate numerical symbols, such as Kanji or Hindi digits, or ordinal number representation. 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 %d, %e, %H, %I, %m, %S, %U, %w, %W, and %y field descriptors always return the date /time field in Latin digits (i.e., 0 through 9). The %O modifier was introduced to support the use for display purposes of non-Latin digits. In the LC_TIME category in localedef, the optional alt_digits keyword is intended for this purpose. As an example, assume the following (partial) localedef source:

alt_digits "";"I";"II";" ";"IV";"V";"VI";" ";" " \ "IX";"X";"XI";" " d_fmt "%e.%Om.%Y"

With the above date, the command

date "+x"

would yield ‘‘3.IX.1991.’’ With the same d_fmt, but without the alt_digits, the command would yield ‘‘3.9.1991.’’

Some of the new options for formatting are from the C Standard {7}. The −u option was introduced to allow portable access to Coordinated Universal Time ( ). The string GMT0 is allowed as an equivalent TZ value to be compatible with all of the systems using the implementation, where this option originated. The %e format field descriptor (adopted from System V) was added because the C Standard {7} descriptors did not provide any way to produce the historical default date output during the first nine days of any month.

September 1991 posix.fail