21.1.7 Examples of date

Here are a few examples. Also see the documentation for the -d option in the previous section.

  • To print the date of the day before yesterday:
    date --date='2 days ago'
  • To print the date of the day three months and one day hence:
    date --date='3 months 1 day'
  • To print the day of year of Christmas in the current year:
    date --date='25 Dec' +%j
  • To print the current full month name and the day of the month:

    date '+%B %d'

    But this may not be what you want because for the first nine days of the month, the ‘%d’ expands to a zero-padded two-digit field, for example ‘date -d 1may '+%B %d'’ will print ‘May 01’.

  • To print a date without the leading zero for one-digit days of the month, you can use the (GNU extension) ‘-’ flag to suppress the padding altogether:
    date -d 1may '+%B %-d'
  • To print the current date and time in the format required by many non-GNU versions of date when setting the system clock:
    date +%m%d%H%M%Y.%S
  • To set the system clock forward by two minutes:
    date --set='+2 minutes'
  • To print the date in Internet RFC 5322 format, use ‘date --rfc-email’. Here is some example output:
    Fri, 09 Sep 2005 13:51:39 -0700
  • To convert a date string to the number of seconds since the epoch (which is 1970-01-01 00:00:00 UTC), use the --date option with the ‘%s’ format. That can be useful in sorting and/or graphing and/or comparing data by date. The following command outputs the number of the seconds since the epoch for the time two minutes after the epoch:

    date --date='1970-01-01 00:02:00 +0000' +%s
    120

    If you do not specify time zone information in the date string, date uses your computer’s idea of the time zone when interpreting the string. For example, if your computer’s time zone is that of Cambridge, Massachusetts, which was then 5 hours (i.e., 18,000 seconds) behind UTC:

    # local time zone used
    date --date='1970-01-01 00:02:00' +%s
    18120
  • If you’re sorting or graphing dated data, your raw date values may be represented as seconds since the epoch. But few people can look at the date ‘946684800’ and casually note “Oh, that’s the first second of the year 2000 in Greenwich, England.”

    date --date='2000-01-01 UTC' +%s
    946684800

    An alternative is to use the --utc (-u) option. Then you may omit ‘UTC’ from the date string. Although this produces the same result for ‘%s’ and many other format sequences, with a time zone offset different from zero, it would give a different result for zone-dependent formats like ‘%z’.

    date -u --date=2000-01-01 +%s
    946684800

    To convert such an unwieldy number of seconds back to a more readable form, use a command like this:

    # local time zone used
    date -d '1970-01-01 UTC 946684800 seconds' +"%Y-%m-%d %T %z"
    1999-12-31 19:00:00 -0500

    Or if you do not mind depending on the ‘@’ feature present since coreutils 5.3.0, you could shorten this to:

    date -d @946684800 +"%F %T %z"
    1999-12-31 19:00:00 -0500

    Often it is better to output UTC-relative date and time:

    date -u -d '1970-01-01 946684800 seconds' +"%Y-%m-%d %T %z"
    2000-01-01 00:00:00 +0000
  • Typically the seconds count omits leap seconds, but some systems are exceptions. Because leap seconds are not predictable, the mapping between the seconds count and a future timestamp is not reliable on the atypical systems that include leap seconds in their counts.

    Here is how the two kinds of systems handle the leap second at 2012-06-30 23:59:60 UTC:

    # Typical systems ignore leap seconds:
    date --date='2012-06-30 23:59:59 +0000' +%s
    1341100799
    date --date='2012-06-30 23:59:60 +0000' +%s
    date: invalid date '2012-06-30 23:59:60 +0000'
    date --date='2012-07-01 00:00:00 +0000' +%s
    1341100800
    # Atypical systems count leap seconds:
    date --date='2012-06-30 23:59:59 +0000' +%s
    1341100823
    date --date='2012-06-30 23:59:60 +0000' +%s
    1341100824
    date --date='2012-07-01 00:00:00 +0000' +%s
    1341100825