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21.1.6 Options for date

The program accepts the following options. Also see Common options.

‘-d datestr’
‘--date=datestr’
Display the date and time specified in datestr instead of the current date and time. datestr can be in almost any common format. It can contain month names, time zones, ‘am’ and ‘pm’, ‘yesterday’, etc. For example, --date="2004-02-27 14:19:13.489392193 +0530" specifies the instant of time that is 489,392,193 nanoseconds after February 27, 2004 at 2:19:13 PM in a time zone that is 5 hours and 30 minutes east of UTC.
Note: input currently must be in locale independent format. E.g., the LC_TIME=C below is needed to print back the correct date in many locales: 
          date -d "$(LC_TIME=C date)"

See Date input formats.

‘-f datefile’
‘--file=datefile’
Parse each line in datefile as with -d and display the resulting date and time. If datefile is ‘-’, use standard input. This is useful when you have many dates to process, because the system overhead of starting up the date executable many times can be considerable.
‘-r file’
‘--reference=file’
Display the date and time of the last modification of file, instead of the current date and time.
‘-R’
‘--rfc-822’
‘--rfc-2822’
Display the date and time using the format ‘%a, %d %b %Y %H:%M:%S %z’, evaluated in the C locale so abbreviations are always in English. For example: 
          Fri, 09 Sep 2005 13:51:39 -0700

This format conforms to Internet RFCs 2822 and 822, the current and previous standards for Internet email.

‘--rfc-3339=timespec’
Display the date using a format specified by Internet RFC 3339. This is a subset of the ISO 8601 format, except that it also permits applications to use a space rather than a ‘T’ to separate dates from times. Unlike the other standard formats, RFC 3339 format is always suitable as input for the --date (-d) and --file (-f) options, regardless of the current locale.

The argument timespec specifies how much of the time to include. It can be one of the following:

‘date’
Print just the full-date, e.g., ‘2005-09-14’. This is equivalent to the format ‘%Y-%m-%d’.
‘seconds’
Print the full-date and full-time separated by a space, e.g., ‘2005-09-14 00:56:06+05:30’. The output ends with a numeric time-offset; here the ‘+05:30’ means that local time is five hours and thirty minutes east of UTC. This is equivalent to the format ‘%Y-%m-%d %H:%M:%S%:z’.
‘ns’
Like ‘seconds’, but also print nanoseconds, e.g., ‘2005-09-14 00:56:06.998458565+05:30’. This is equivalent to the format ‘%Y-%m-%d %H:%M:%S.%N%:z’.

‘-s datestr’
‘--set=datestr’
Set the date and time to datestr. See -d above.
‘-u’
‘--utc’
‘--universal’
Use Coordinated Universal Time (UTC) by operating as if the TZ environment variable were set to the string ‘UTC0’. Coordinated Universal Time is often called “Greenwich Mean Time” (gmt) for historical reasons.