Time and date command in linux

LFCA: Learn to Manage Time and Date in Linux – Part 6

This article is Part 6 of the LFCA series, here in this part, you will acquaint yourself with the general system administration commands to manage time and date settings in the Linux system.

Time is crucial in any Linux system. Multiple services such as crontab, anacron, backup and restore services depend on accurate time to carry out their tasks as expected.

Linux has 2 types of clocks:

• Hardware clock – This is the battery-powered clock also referred to as the CMOS clock or RTC ( Real Time Clock). The clock runs independently of the operating system & keeps running even when the system is powered off provided the CMOS battery is present.
• System clock ( Software clock ) – This is also referred to as the kernel clock. At boot time, the system clock is initialized from the hardware clock and takes over from there.

Usually, there exists a time difference between the two clocks such that they gradually drift from each other. We will come to this later and show you how you can sync these clocks.

For now, we will see how you can check time and date on a Linux system.

Check Time and Date On a Linux System

There are two main utilities used to check time and date on a Linux system. The first is the date command. Without any arguments, it provides quite a bit of information shown

$ date Friday 26 March 2021 11:15:39 AM IST 

To view the date in dd-mm-yy time format only, execute the command:

$ date +"%d-%m-%y" 26-03-21 

If you just want to view the current time only and nothing else, use the command:

$ date "+%T" 11:17:11 

The timedatectl command is a new utility used in modern Linux systems such as Ubuntu 18.04, RHEL 8 & CentOS 8. It’s a replacement of the date command which was prominent in the old SysVinit systems. It can be used to query and adjust the time on a Linux system.

Without any options, the timedatectl command prints out an array of information such as the local time, UTC time, RTC time, and the timezone to mention a few.

How to Set a Timezone on a Linux System

On a Linux system, time is dependent on the timezone that is set. To check the timezone that is configured on your system, issue the command:

From the output in the snippet above, I am in the Africa/Nairobi timezone. To view the available timezones, run the command:

$ timedatectl list-timezones

Press ENTER to scroll through the whole list of the possible time zones that are available.

Timezones are also defined in the /usr/share/zoneinfo/ path as shown.

There are a couple of ways that you can use to configure the timezone. Using the timedatectl command, you can set the timezone, for instance, to America/Chicago, using the syntax shown.

$ timedatectl set-timezone 'America/Chicago'

The other way you can set the timezone is to create a symbolic link from a timezone file in the /usr/share/zoneinfo path to /etc/localtime. For example, to set the local time zone to EST (Eastern Standard Time), issue the command:

$ sudo ln -sf /usr/share/zoneinfo/EST /etc/localtime

Set Date and Time on a Linux System

To set time only on a Linux system using the format HH:MM:SS (Hour: Minute: Second ), use the syntax below

$ timedatectl set-time 18:30:45

To set the date only in YY-MM-DD (Year: Month: Day) format, use the syntax:

$ timedatectl set-time 20201020

To set both date and time, run:

$ timedatectl set-time '2020-10-20 18:30:45'

NOTE: Manually setting time and date in this manner is not recommended since you are likely to configure inaccurate time and date settings. In fact, by default, automatic time synchronization is turned on to prevent you from making manual time and date settings.

The most recommended way to set time is by either specifying the time zone that you are in as shown earlier or turning on automatic time synchronization with a remote NTP server.

Set Automatic Time Synchronization using NTP Server

NTP is short for Network Time Protocol, which is an internet protocol that is used to automatically synchronize the system’s time clock with a pool on online NTP servers.

Using the timedatectl command, you can set automatic time synchronization as follows:

To disable automatic NTP time synchronization, execute:

Conclusion

The timedatectl and date commands are handy command-line tools that can help you check and adjust your time on Linux.

This is James, a certified Linux administrator and a tech enthusiast who loves keeping in touch with emerging trends in the tech world. When I’m not running commands on the terminal, I’m taking listening to some cool music. taking a casual stroll or watching a nice movie.

Each tutorial at TecMint is created by a team of experienced Linux system administrators so that it meets our high-quality standards.

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1 thought on “LFCA: Learn to Manage Time and Date in Linux – Part 6”

“The timedatectl command is a new utility used in MODERN Linux systems such as Ubuntu 18.04, RHEL 8 & CentOS 8. It’s a replacement of the date command which was prominent in the OLD SysVinit systems.” (emphases mine) That statement insinuates that systemd is the new standard and SysVinit, and other non-systemd inits, are totally deprecated, which is very far from the truth. Whether a Linux distro is Modern or OLD is determined by the kernel version it uses, not the version of any of the distro’s components, even if it is the init. There still are many MODERN Linux systems, such as Gentoo, PCLinuxOS, Devuan, Artix, and others that use SysVinit, runit, or other inits rather than systemd. BTW – Ubuntu 18.04 can in no way be considered MODERN as Ubuntu 21.04 has been already released. “There are two main utilities used to check time and date on a Linux system.” You should differentiate right up front which command is used by distros using systemd as init and which command is used by distros using non-systemd inits. Somehow you did not provide the “date” command options for setting time zone, date & time, and how to sync with NTP servers. Reply

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Date Command in Linux: How to Set, Change, Format and Display Date

Linux date command displays and sets the system date and time. This command also allows users to print the time in different formats and calculate future and past dates.

Read on to learn how to use the date command in Linux.

• A system running Linux
• A user account with root privileges
• Access to a terminal window/command line

Linux date Command Syntax

The syntax for the date command is:

How to Use date Command in Linux

To show the current system time and date, type in the date command:

The output displays the day of the week, day of the month, month, year, current time, and time zone. By default, the date command is set to the time zone of the operating system.

The -d option allows users to operate on a specific date. For example, we can type in the following command:

You can use the —date command to display the given date string in the format of a date. This command does not affect the system’s actual date and time values, and it only prints the requested date. For example:

Note: Learn how can you create a script using the printf command to display the current date.

Linux date Command Format Options

To format the date command’s output, you can use control characters preceded by a + sign. Format controls begin with the % symbol and are substituted by their current values.

Here, the %Y character is replaced with the current year, %m with month, and %d with the day of the month:

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

Here are another two formatting examples:

date +"Week number: %V Year: %y"

These are the most common formatting characters for the date command:

• • %D – Display date as mm/dd/yy
  • %Y – Year (e.g., 2020)
  • %m – Month (01-12)
  • %B – Long month name (e.g., November)
  • %b – Short month name (e.g., Nov)
  • %d – Day of month (e.g., 01)
  • %j – Day of year (001-366)
  • %u – Day of week (1-7)
  • %A – Full weekday name (e.g., Friday)
  • %a – Short weekday name (e.g., Fri)
  • %H – Hour (00-23)
  • %I – Hour (01-12)
  • %M – Minute (00-59)
  • %S – Second (00-60)

  To see all formatting options, run date —help or the man command man date in your terminal.

  Set or Change Date in Linux

  To change the system clock manually, use the set command. For example, to set the date and time to 5:30 PM, May 13, 2010, type:

  

  Most Linux distributions have the system clock synchronized using the ntp or the systemd-timesyncd services, so be careful when the setting the clock manually.

  Display Past Dates

  Use the —date option to display past dates in Linux. The date command accepts values such as «tomorrow» , «Friday» , «last Friday» , «next Friday» , «next week» , and similar. So, use the following strings to print past dates::

  

  

  

  Display Future Dates

  The —date option can also display future dates. Like with past dates, you can type in strings to print upcoming dates:

  

  

  

  Display the Date String at Line of File

  The —file option prints the date string present at each line of the file. Unlike the —date option, —file can present multiple date strings at each line.

  This is the syntax for the —file command:

  Here we use the cat command to add dates to a file and then print them with the date command:

  

  Display Last Modified Timestamp of a Date File

  When you use the -r option, the date command prints the last modification time of a file. For example, the following command prints the last time the hosts file was changed:

  

  Override a Time Zone

  By default, the date command uses the time zone defined in /etc/localtime . To use a different time zone in the environment, set the TZ variable to the desired time zone.

  For example, to switch to New York time, enter:

  

  Type in the date command to return the system to its default time zone. To see all available time zones, use the timedatectl list-timezones command.

  The date command can also show the local time for a different time zone. For example, to display the local time for 4:30 PM next Monday on the Australian east coast, type:

  date -d 'TZ="Australia/Sydney" 04:30 next Monday'

  

  Use date with Other Commands

  You can use the date command to create file names that contain the current time and date. The input below creates a backup MySQL file in the format of the current date:

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

  Another common use of the date command is in shell scripts. Below we assign the output of date to the date_now variable:

  

  Use Unix Epoch Time (Epoch Converter)

  You can use the date command as an Epoch converter. Epoch, or Unix timestamps, is the number of seconds that have passed since January 1, 1970, at 00:00:00 UTC.

  To show the number of seconds from the epoch to the current day, use the %s format control:

  

  To see how many seconds passed from epoch to a specific date, enter:

  

  You now have a good understanding of how to use the date command in Linux. If you are interested in more date/time configuration options for Linux, read How to Set or Change Timezone/Date/Time on Ubuntu.

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  How can I get the current date and time in the terminal and set a custom command in the terminal for it? [closed]

  Closed. This question does not meet Stack Overflow guidelines. It is not currently accepting answers.

  This question does not appear to be about a specific programming problem, a software algorithm, or software tools primarily used by programmers. If you believe the question would be on-topic on another Stack Exchange site, you can leave a comment to explain where the question may be able to be answered.

  I have to check the time in a Linux terminal. What is the command for getting date and time in a Linux terminal? Is there a way in which we can set a custom function?

  This question seems on topic as it relates to a specific computing task on a specific operating system (which is just a software layer itself). As, @drstevens said, this is the first result in Google and it was informative for me needs. If it were off-topic, it would read something like «Do operating systems tell time?» or «What do you guys think about operating systems that tell time.» Stack Overflow is a great resource for beginners and it seems like this was closed as for being too beginner of a question. It should instead just be listed as a beginner question.

  StackExchange is the place for answers. This is a good question. Perhaps the question should be migrated, but it should not be closed, in my opinion. This question appeared first in my Google results when I searched for «linux check time».

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