Intro To 'date' Command In Linux

2023-05-15 - By Robert Elder

I use the 'date' command to print the current date:

date

Fri 12 May 2023 12:14:05 PM EDT

Custom Time Zones With The 'date' Command

By default, the 'date' command will print the current date in the current time zone. You can include the '--utc' flag to see the date printed in coordinated universal time:

date --utc

Fri 12 May 2023 04:14:18 PM UTC

Or, you can explicitly specify a time zone in the 'TZ' shell variable like this:

TZ='America/Los_Angeles' date

Fri 12 May 2023 09:14:41 AM PDT

Custom Format Strings With The 'date' Command

I can also use a custom date format string to print out the date in any way that I want like this:

date +"%Y-%m-%d %H:%M:%S"

2023-05-12 12:17:15

or like this:

date +"%Y___%m____%d %H--%M------%S"

2023___05____12 12--17------31

Relative Dates With The 'date' Command

The 'date' command will print the date from 10 days in the past using this command:

date --date="10 days ago"

Tue 02 May 2023 12:23:38 PM EDT

Using The 'date' Command With Unix Timestamp

The 'date' command also lets you specify a date using a Unix timestamp by placing an '@' symbol before the number like this:

date --date="@1677476463"

Mon 27 Feb 2023 12:41:03 AM EST

or like this:

date --date="@1"

Wed 31 Dec 1969 07:00:01 PM EST

date --date="@1" --utc

Thu 01 Jan 1970 12:00:01 AM UTC

More 'date' Command Format Specifier Documentation

The 'date' command supports many other flags and format strings that can be found in the 'man' pages:

man date

       FORMAT controls the output.  Interpreted sequences are:

       %%     a literal %
       %a     locale's abbreviated weekday name (e.g., Sun)
       %A     locale's full weekday name (e.g., Sunday)
       %b     locale's abbreviated month name (e.g., Jan)
       %B     locale's full month name (e.g., January)
       %c     locale's date and time (e.g., Thu Mar  3 23:05:25 2005)
       %C     century; like %Y, except omit last two digits (e.g., 20)
       %d     day of month (e.g., 01)
       %D     date; same as %m/%d/%y
       %e     day of month, space padded; same as %_d
       %F     full date; same as %Y-%m-%d
       %g     last two digits of year of ISO week number (see %G)
       %G     year of ISO week number (see %V); normally useful only with %V
       %h     same as %b
       %H     hour (00..23)
       %I     hour (01..12)
       %j     day of year (001..366)
       %k     hour, space padded ( 0..23); same as %_H
       %l     hour, space padded ( 1..12); same as %_I
       %m     month (01..12)
       %M     minute (00..59)
       %n     a newline
       %N     nanoseconds (000000000..999999999)
       %p     locale's equivalent of either AM or PM; blank if not known
       %P     like %p, but lower case
       %q     quarter of year (1..4)
       %r     locale's 12-hour clock time (e.g., 11:11:04 PM)
       %R     24-hour hour and minute; same as %H:%M
       %s     seconds since 1970-01-01 00:00:00 UTC
       %S     second (00..60)
       %t     a tab
       %T     time; same as %H:%M:%S
       %u     day of week (1..7); 1 is Monday
       %U     week number of year, with Sunday as first day of week (00..53)
       %V     ISO week number, with Monday as first day of week (01..53)
       %w     day of week (0..6); 0 is Sunday
       %W     week number of year, with Monday as first day of week (00..53)
       %x     locale's date representation (e.g., 12/31/99)
       %X     locale's time representation (e.g., 23:13:48)
       %y     last two digits of year (00..99)
       %Y     year
       %z     +hhmm numeric time zone (e.g., -0400)
       %:z    +hh:mm numeric time zone (e.g., -04:00)
       %::z   +hh:mm:ss numeric time zone (e.g., -04:00:00)
       %:::z  numeric time zone with : to necessary precision (e.g., -04, +05:30)
       %Z     alphabetic time zone abbreviation (e.g., EDT)
       By default, date pads numeric fields with zeroes.  The following optional flags may follow '%':
       -      (hyphen) do not pad the field
       _      (underscore) pad with spaces
       0      (zero) pad with zeros
       ^      use upper case if possible
       #      use opposite case if possible

       After any flags comes an optional field width, as a decimal number; then an optional modifier, which is either E to use the locale's alternate  representations  if  available, or O to use the locale's alternate numeric symbols if available.

or also the 'info' pages:

info date

21.1.1 Time conversion specifiers
---------------------------------

‘date’ conversion specifiers related to times.

‘%H’
     hour (‘00’...‘23’)
‘%I’
     hour (‘01’...‘12’)
‘%k’
     hour, space padded (‘ 0’...‘23’); equivalent to ‘%_H’.  This is a
     GNU extension.
‘%l’
     hour, space padded (‘ 1’...‘12’); equivalent to ‘%_I’.  This is a
     GNU extension.
‘%M’
     minute (‘00’...‘59’)
‘%N’
     nanoseconds (‘000000000’...‘999999999’).  This is a GNU extension.
‘%p’
     locale’s equivalent of either ‘AM’ or ‘PM’; blank in many locales.
     Noon is treated as ‘PM’ and midnight as ‘AM’.
‘%P’
     like ‘%p’, except lower case.  This is a GNU extension.
‘%r’
     locale’s 12-hour clock time (e.g., ‘11:11:04 PM’)
‘%R’
     24-hour hour and minute.  Same as ‘%H:%M’.
‘%s’
     seconds since the epoch, i.e., since 1970-01-01 00:00:00 UTC.  Leap
     seconds are not counted unless leap second support is available.
     *Note %s-examples::, for examples.  This is a GNU extension.
‘%S’
     second (‘00’...‘60’).  This may be ‘60’ if leap seconds are
     supported.
‘%T’
     24-hour hour, minute, and second.  Same as ‘%H:%M:%S’.
‘%X’
     locale’s time representation (e.g., ‘23:13:48’)
‘%z’
     Four-digit numeric time zone, e.g., ‘-0600’ or ‘+0530’, or ‘-0000’
     if no time zone is determinable.  This value reflects the numeric
     time zone appropriate for the current time, using the time zone
     rules specified by the ‘TZ’ environment variable.  A time zone is
     not determinable if its numeric offset is zero and its abbreviation
     begins with ‘-’.  The time (and optionally, the time zone rules)
     can be overridden by the ‘--date’ option.
‘%:z’
     Numeric time zone with ‘:’, e.g., ‘-06:00’ or ‘+05:30’), or
     ‘-00:00’ if no time zone is determinable.  This is a GNU extension.
‘%::z’
     Numeric time zone to the nearest second with ‘:’ (e.g., ‘-06:00:00’
     or ‘+05:30:00’), or ‘-00:00:00’ if no time zone is determinable.
     This is a GNU extension.
‘%:::z’
     Numeric time zone with ‘:’ using the minimum necessary precision
     (e.g., ‘-06’, ‘+05:30’, or ‘-04:56:02’), or ‘-00’ if no time zone
     is determinable.  This is a GNU extension.
‘%Z’
     alphabetic time zone abbreviation (e.g., ‘EDT’), or nothing if no
     time zone is determinable.  See ‘%z’ for how it is determined.

21.1.2 Date conversion specifiers
---------------------------------

‘date’ conversion specifiers related to dates.

‘%a’
     locale’s abbreviated weekday name (e.g., ‘Sun’)
‘%A’
     locale’s full weekday name, variable length (e.g., ‘Sunday’)
‘%b’
     locale’s abbreviated month name (e.g., ‘Jan’)
‘%B’
     locale’s full month name, variable length (e.g., ‘January’)
‘%c’
     locale’s date and time (e.g., ‘Thu Mar  3 23:05:25 2005’)
‘%C’
     century.  This is like ‘%Y’, except the last two digits are
     omitted.  For example, it is ‘20’ if ‘%Y’ is ‘2000’, and is ‘-0’ if
     ‘%Y’ is ‘-001’.  It is normally at least two characters, but it may
     be more.
‘%d’
     day of month (e.g., ‘01’)
‘%D’
     date; same as ‘%m/%d/%y’
‘%e’
     day of month, space padded; same as ‘%_d’
‘%F’
     full date in ISO 8601 format; same as ‘%Y-%m-%d’.  This is a good
     choice for a date format, as it is standard and is easy to sort in
     the usual case where years are in the range 0000...9999.
‘%g’
     year corresponding to the ISO week number, but without the century
     (range ‘00’ through ‘99’).  This has the same format and value as
     ‘%y’, except that if the ISO week number (see ‘%V’) belongs to the
     previous or next year, that year is used instead.
‘%G’
     year corresponding to the ISO week number.  This has the same
     format and value as ‘%Y’, except that if the ISO week number (see
     ‘%V’) belongs to the previous or next year, that year is used
     instead.  It is normally useful only if ‘%V’ is also used; for
     example, the format ‘%G-%m-%d’ is probably a mistake, since it
     combines the ISO week number year with the conventional month and
     day.
‘%h’
     same as ‘%b’
‘%j’
     day of year (‘001’...‘366’)
‘%m’
     month (‘01’...‘12’)
‘%q’
     quarter of year (‘1’...‘4’)
‘%u’
     day of week (‘1’...‘7’) with ‘1’ corresponding to Monday
‘%U’
     week number of year, with Sunday as the first day of the week
     (‘00’...‘53’).  Days in a new year preceding the first Sunday are
     in week zero.
‘%V’
     ISO week number, that is, the week number of year, with Monday as
     the first day of the week (‘01’...‘53’).  If the week containing
     January 1 has four or more days in the new year, then it is
     considered week 1; otherwise, it is week 53 of the previous year,
     and the next week is week 1.  (See the ISO 8601 standard.)
‘%w’
     day of week (‘0’...‘6’) with 0 corresponding to Sunday
‘%W’
     week number of year, with Monday as first day of week
     (‘00’...‘53’).  Days in a new year preceding the first Monday are
     in week zero.
‘%x’
     locale’s date representation (e.g., ‘12/31/99’)
‘%y’
     last two digits of year (‘00’...‘99’)
‘%Y’
     year.  This is normally at least four characters, but it may be
     more.  Year ‘0000’ precedes year ‘0001’, and year ‘-001’ precedes
     year ‘0000’.

Consult the actual 'info' pages for even more format specifiers.

And that's why the 'date' command is my favourite Linux command.

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