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Linux Date Command

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The date command displays the current date and time. It can also be used to display a date in a format you specify. The super-user (root) can use it to set the system clock.

Contents

Usage

With no options, the date command displays the current system date and time, including day-of-week, month, time, timezone, and year. For example:

$ date
Wed Aug 18 16:24:44 EDT 2010

To operate on a specific date, you can provide one with the -d flag. For example:

$ date -d "1974-01-04"
Fri Jan  4 00:00:00 EST 1974

date has many display formatting options. Provide date with the formatting string by prefixing it with a plus sign as follows:

$ date +"Week number: %V Year: %y"
Week number: 33 Year: 10

The format string is then outputted with each formatting token substituted by its value. %V is the formatting option to display the current week number, and %y represents the last two digits of the year.

Formatting Options

Here's a small sample of the formatting tokens date supports:

%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)
%F   full date; same as %Y-%m-%d
%s   seconds since 1970-01-01 00:00:00 UTC

Running date --help will display the list of formatting options, while man date will show you the entire man page with much more detail.

Override the Timezone

By default, date uses the timezone defined in /etc/localtime. The environment variable TZ can be used to override this behavior. For example:

$ TZ=GMT date
Fri Aug 20 15:15:36 GMT 2010

Valid timezones are defined in /usr/share/zoneinfo/.

Examples

The following examples illustrate how you can use the date command to find the date and time at various points in time.

$ date -d now
Wed Aug 18 16:47:31 EDT 2010
$ date -d today
Wed Aug 18 16:47:32 EDT 2010
$ date -d yesterday
Tue Aug 17 16:47:33 EDT 2010
$ date -d tomorrow
Thu Aug 19 16:46:34 EDT 2010
$ date -d sunday
Sun Aug 22 00:00:00 EDT 2010
$ date -d last-sunday
Sun Aug 15 00:00:00 EDT 2010

Other valid date time strings include: last-week, next-week, last-month, next-month, last-year, and next-year.

Seconds from epoch

date has other surprising uses. For example, it can be used to convert a given date/time to Unix epoch time (seconds since 00:00:00, Jan 1, 1970) and back. The following example will show you the seconds from epoch to the current time:

$ date +%s
1282163756

Seconds from epoch to the provided date/time

$ date -d "1974-01-04" +"%s"
126507600

Convert epoch to a date

$ date -d "UTC 1970-01-01 126507600 secs"
Fri Jan  4 00:00:00 EST 1974

$ date -d @126507600
Fri Jan  4 00:00:00 EST 1974

Determine which day of the week a given date was

$ date -d "1974-01-04" +"%A"
Friday

Using date in Scripts and Commands

You can assign the output of date to a shell variable and then use it later in your scripts. For instance:

$ STARTTIME=`date`
$ echo $STARTTIME
Fri Aug 20 11:46:48 EDT 2010
$ sleep 5
$ echo $STARTTIME
Fri Aug 20 11:46:48 EDT 2010

You can also use date to create filenames that contain the current day.

tar cfz /backup-`date +%F`.tar.gz /home/caker/

This would tar and gzip the files in /home/caker/ into a filename called backup-2010-08-20.tar.gz.

Setting the Date

Setting the date should not be needed if you're running ntpd to keep good time and have set your timezone correctly. However, if you find you need to set the system clock, here's an example:

date --set="20101231 23:59"
Creative Commons License

This guide is licensed under a Creative Commons Attribution-NoDerivs 3.0 United States License.

Last edited by System on Tuesday, April 19th, 2011 (r41).