date Command in Linux Explained [with Examples]

Last updated: October 23, 2023 | Bobbin Zachariah

The date command in Linux is used for displaying, setting, or manipulating the system date and time. It also allows users to display time in various formats and calculates the past and future dates. In order to change the date and time you should need a user with root or sudo privileges.

Syntax

The basic syntax of date command:

date [option]... [+format]

Where format is a sequence of characters that specifies how the date and time are formatted.

Options

Useful options of date command:

  • -d, --date=STRING : Display time represented by the STRING.
  • -f, --file=DATEFILE: Parse a file and display date and time.
  • -I, --iso-8601[=TIMESPEC]: Display date and time in ISO 8601 format.
  • -r, --reference=FILE: Display the last modification time of FILE.
  • -R, --rfc-2822: Display date and time in RFC format.
  • -s, --set=STRING: Set the time represented by STRING.
  • -u, --utc, --universal: Display in UTC time.

Basic Usage

By default date command displays the current date and time in the default format.

Command:

date
date command

The default date format depends on the LC_TIME defined in locale. Locale files are typically stored in /usr/share/i18n/locales/ and directives d_t_fmt, d_fmt, and t_fmt specify the formats for date and time, date only, and time only, respectively.

Date in Custom Formats

The displayed terminal output of the Linux date command can be formatted using format control characters which are preceded by a ‘+’ symbol. All these format controls proceed with the ‘%’ sign and are followed by their values.

Example:

date +"Year: %Y, Month: %m, Day: %d"
format custom date

To display the date in the format of YYYY-MM-DD:

date +%Y-%m-%d
another date format example

Formatting characters:

  • %a - Prints weekday’s name in short format (e.g., Mon).
  • %A - Used to display full weekday name (e.g., Monday).
  • %b - Display the name of the month in short form (e.g., Jan).
  • %B - Used to display the full month’s name (e.g., January).
  • %d - Displays the month’s day (e.g., 05).
  • %H - Display Hour (00..23).
  • %I - Display Hour in (01..12) format.
  • %j - Displays the Day of the year (001..366).
  • %m - Displays Month in number (01..12).
  • %M - Print Minutes in 00..59 sec.
  • %S - Displays seconds (00..60).
  • %u - Display week’s day in number (1..7).
  • %Y - Used to display Full-year (e.g., 2019).

Examples

Let's look into some useful examples of date command

1. Getting the date of the day in future or past

To print tomorrow’s date, type the following command:

date -d "tomorrow"
date format tomorrow in Linux

Display the next Friday date:

date -d "next Friday"
date format next Friday in Linux

To display the date and time from exactly one year ago from the current date:

date -date "1 year ago"

Display the yesterday date:

date -d "yesterday"

Similarly, to display the last Friday date:

date -d "last Friday"

2. Reading date from a string

Display the specific date and time "2020-10-09 10:22:47", rather than the current date and time.

date -d "2020-10-09 10:22:47"
date reading from a string

Include customization to it:

date -d "12 Jan 2021" +"%A, %d %B %Y"
date reading from a string including formatting

3. Show the last modification time of a file

To display the last modification date of the ‘/etc/hosts’ file:

date -r /etc/hosts
using date command get files last modification time

4. Using as an Epoch converter

To display the current date and time in seconds since the Unix Epoch (January 1, 1970 00:00:00 GMT):

date +%s
current date epoch

This displays the number of seconds since the Unix Epoch (00:00:00 UTC on 1 January 1970) for the date October 25, 1980.

date -d "1980-10-25" +"%s"

5. Set a date

To manually set the date and time to 2:30 PM, October 13, 2021:

sudo date --set="20211013 05:30"

Note: In most modern Linux distributions, the system time is usually synchronized with NTP, often through the systemd-timesyncd service or other similar services.

6. Display output in ISO 8601 format

To outputs the current date and time up to seconds precision, and includes the timezone information.

date --iso-8601=seconds
date in ISO 8601 format

7. Display output in RFC 3339 format

This displays the current date and time up to the precision of seconds, formatted according to the Internet-standard RFC 3339:

date --rfc-3339=seconds
date in RFC 3339 format

8. Using date with other commands

To create a backup of a MySQL database with a filename containing the current date:

mysqldump database_name > database_name-$(date +%Y%m%d).sql

Here the date command is used to assign the current date and time to a variable in a specific format:

$ date_current=$(date "+%F-%H-%M-%S")
$ echo $date_current
SHARE

Comments

Please add comments below to provide the author your ideas, appreciation and feedback.

Leave a Reply

Leave a Comment