Change Date, Time, Timezone, Format, NTP in Linux

Management of system data and time is very important in the world of Linux which provides a set of powerful commands to sync clock with the time server or adjustment of the data and time manually. In this detailed guide, we will discuss various methods and ways to work with Linux data and time systems.

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Date and Time Management in Linux

Linux depends on a system clock which keeps track of data and time, it can be set or adjusted by using various commands and tools. The Data and Time should be kept accurate which is crucial for tasks like log file timestamps, scheduling tasks, and synchronized communication between systems.

 

Common Use Cases for Changing Date and Time

Following are a few of the scenarios in which we might need to control or adjust the Linux system’s data and time:

• Correcting an incorrect system clock.
• Synchronizing the system’s time with a time server (NTP).
• Setting a future or past date and time for testing purposes.
• Adjustment of time zones for travelling or working with remote systems placed at different time zones.

 

Using the date Command

The date command is used to change the date and time on a Linux system. It can be used to display and set both the date and time. Let’s have a look at some commonly used options:

 

1. Displaying the Current Date and Time

To print the current date and time we can simply type the data command at the terminal:

date

Output:

Thu Aug 09 15:30:00 UTC 2021

 

2. Change the Date and Time

We can use the date command to set a new date and time in the following format:

sudo date -s "YYYY-MM-DD HH:MM:SS"

Just replace YYYY-MM-DD with the required date and HH:MM:SS time in 24-hour format. For example, to set the date to August 10, 2022, at 14:30:00, you would enter:

sudo date -s "2022-08-10 14:30:00"

Make sure to use sudo to change the system time as this operation requires administrative privileges.

 

3. How to Change the Date format on Linux?

You can change the date format in Linux using the date command with the +% format specifier. For example, to display the date in the format “YYYY-MM-DD”, use:

date +%Y-%m-%d

This will show the date in the desired format like:

2021-08-19

 

Synchronizing Time with NTP

NTP (Network Time Protocol) is a widely used protocol used to synchronize the system time with remote time servers. In Linux, the timedatectl command is used for managing time settings and NTP configuration.

 

1. Checking NTP Status

To check the NTP synchronization status, use:

timedatectl status

It will display information about whether NTP synchronization is active or not.

Output:

               Local time: Thu 2021-08-19 15:30:00 UTC
           Universal time: Thu 2021-08-19 15:30:00 UTC
                 RTC time: Thu 2021-08-19 15:30:00
                Time zone: UTC (UTC, +0000)
 System clock synchronized: yes
              NTP service: active
          RTC in local TZ: no

Where each property provides following information:

• Local time: Current local time on the system.
• Universal time: Current time in Coordinated Universal Time (UTC).
• RTC time: Time stored in the hardware clock (Real-Time Clock).
• Time zone: System’s current time zone, in this case, UTC (Universal Coordinated Time).
• System clock synchronized: If the system clock is synchronized with an NTP server, where “yes” means synchronized.
• NTP service: If NTP (Network Time Protocol) service is active.
• RTC in local TZ: If the hardware clock is set to the local time zone, here “no” means it’s set to UTC.

 

2. How to Enabe NTP Synchronization?

To enable NTP synchronization, we can use which will enable automatic time synchronization with NTP servers.

sudo timedatectl set-ntp true

 

3. Manually Setting NTP Servers

We can manually set NTP servers by editing the /etc/systemd/timesyncd.conf file as shown below:

[Time]
NTP=server1.example.com server2.example.com

You can replace server1.example.com and server2.example.com with the addresses of preferred NTP servers.

 

How to Change Time Zone on Linux?

When travelling or working with remote systems in different regions, we need to change the time zones. Linux provides the timedatectl command to manage time zones:

 

1. How to List Available Time Zones

To list available time zones we can use:

timedatectl list-timezones

The output will look like this:

Africa/Abidjan
Africa/Accra
Africa/Addis_Ababa
Africa/Algiers
...
Pacific/Wallis
UTC

 

2. How to set a Time Zone in Linux

To set a new time zone we use following command:

sudo timedatectl set-timezone <your-timezone>

Just replace <your-timezone> with the desired time zone, for example, America/New_York.

 

How to Set Hardware Clock to the Current System Time in Linux?

For setting the hardware clock which is also known as the BIOS clock to the current system time in Linux, we can use the hwclock command as shown below:

sudo hwclock --systohc

It will synchronize the hardware clock with the system time.

 

How to Set the Hardware Clock to UTC on Linux?

To set the hardware clock to UTC (Coordinated Universal Time) on Linux, use the timedatectl command:

sudo timedatectl set-local-rtc 0

 

How to Synchronize System Clock with NTP Servers on Linux?

We can synchronize the system clock with NTP servers on Linux by using the timedatectl command. It will configure your system to automatically synchronize its time with NTP servers.

sudo timedatectl set-ntp true

 

How do Persist Date and Time Changes Across Reboots on Linux?

To persist the data and time across reboots in Linux, we need to set the hardware clock to the current system time by using the hwclock command with the --systohc option.

sudo hwclock --systohc

This ensures that the hardware clock is updated with the correct time during shutdown or reboot, and the changes are retained.