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21.1.3 Options for date

The program accepts the following options. Also see Common options. Except for -u, these options are all GNU extensions to POSIX.

All options that specify the date to display are mutually exclusive. I.e.: --date, --file, --reference, --resolution.

‘-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="2020-07-21 14:19:13.489392193 +0530" specifies the instant of time that is 489,392,193 nanoseconds after July 21, 2020 at 2:19:13 PM in a time zone that is 5 hours and 30 minutes east of UTC.
The datestr must be in locale independent format. E.g., the ‘LC_TIME=C’ below is needed to print the correct date in many locales:

date -d "$(LC_TIME=C date)"

See Date input formats.

‘--debug’ ¶

Annotate the parsed date, display the effective time zone, and warn about potential misuse.

‘-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.

‘-I[timespec]’ ¶

‘--iso-8601[=timespec]’

Display the date using an ISO 8601 format, ‘%Y-%m-%d’.

The argument timespec specifies the number of additional terms of the time to include. It can be one of the following:

‘auto’

Print just the date. This is the default if timespec is omitted. This is like the format %Y-%m-%d.

‘hours’

Also print hours and time zone. This is like the format %Y-%m-%dT%H%:z.

‘minutes’

Also print minutes. This is like the format %Y-%m-%dT%H:%M%:z.

‘seconds’

Also print seconds. This is like the format %Y-%m-%dT%H:%M:%S%:z.

‘ns’

Also print nanoseconds. This is like the format %Y-%m-%dT%H:%M:%S,%N%:z.

This format is always suitable as input for the --date (-d) and --file (-f) options, regardless of the current locale.

‘-r file’ ¶

‘--reference=file’

Display the date and time of the last modification of file, instead of the current date and time.

‘--resolution’ ¶

Display the timestamp resolution instead of the time. Current clock timestamps that are output by date are integer multiples of the timestamp resolution. With this option, the format defaults to ‘%s.%N’. For example, if the clock resolution is 1 millisecond, the output is:

0.001000000

‘-R’ ¶

‘--rfc-email’

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:

Mon, 09 Jul 2020 17:00:00 -0400

This format conforms to Internet RFCs 5322, 2822 and 822, the current and previous standards for Internet email. For compatibility with older versions of date, --rfc-2822 and --rfc-822 are aliases for --rfc-email.

‘--rfc-3339=timespec’ ¶

Display the date using a format specified by Internet RFC 3339. This is like --iso-8601, except that a space rather than a ‘T’ separates dates from times, and a period rather than a comma separates seconds from subseconds. This 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., ‘2020-07-21’. This is like the format ‘%Y-%m-%d’.

‘seconds’

Print the full-date and full-time separated by a space, e.g., ‘2020-07-21 04:30:37+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 like the format ‘%Y-%m-%d %H:%M:%S%:z’.

‘ns’

Like ‘seconds’, but also print nanoseconds, e.g., ‘2020-07-21 04:30:37.998458565+05:30’. This is like the format ‘%Y-%m-%d %H:%M:%S.%N%:z’.

‘-s datestr’ ¶

‘--set=datestr’

Set the date and time to datestr. See -d above. See also Setting the time.

‘-u’ ¶

‘--utc’

‘--universal’

Use Universal Time by operating as if the TZ environment variable were set to the string ‘UTC0’. UTC stands for Coordinated Universal Time, established in 1960. Universal Time is often called “Greenwich Mean Time” (GMT) for historical reasons. Typically, systems ignore leap seconds and thus implement an approximation to UTC rather than true UTC.