Here are a few examples. Also see the documentation for the
option in the previous section.
date --date='2 days ago'
date --date='3 months 1 day'
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 ‘
-’ flag to suppress the padding altogether:
date -d 1may '+%B %-d'
datewhen setting the system clock:
date --set='+2 minutes'
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
%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
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
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 ‘
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