Setting the date and time in CentOS

Contents
Introduction
date: Find out the current system date and time
hwclock: Find out the current BIOS date and time
Change the date and time manually
Synchronization with ntp
Force the system to synchronize time with ntp
Timezone

Introduction

When working on the network, time and date synchronization is an important factor that increases stability and safety the work of all systems.

In this article, you will learn how to set the date and time manually. And, what's more the important thing is how to synchronize them with the ntp server.

These are articles about the date and time in CentOS 7.

About the date and time in Rocky Linux and CentOS 8 read here

Find out the current system time

To find out the current system time, you can use the command date

date

2024-03-29 00:03:57.364911+02:00

Find out the current BIOS time

To find out the current BIOS system time, you can use the command hwclock

sudo hwclock

2024-03-29 00:03:57.389911+02:00

date и hwclock they can show completely different times

Fix the current time

First you need to set the time with the command date

date MMDDhhmmCCYY.ss

Description of the date command parameters:
MM two digits of the current month (example: January=01);
DD two digits of the current date (if the current calendar day is 1, then 01 is written);
hh two digits indicating the hour
mm two digits denoting minutes
CCYY four digits of the year
ss two digits of seconds

You can also enter «date MMDDhhmmCCYY» without seconds, then seconds are set to zero.

After executing date, you need to enter a new set time in the BIOS:

hwclock --systohc

Now it remains only to check whether the changes have been saved

sudo hwclock

Synchronization with ntp

Check if ntp is installed with the command

which ntpd

/usr/sbin/ntpd

If ntp is not installed execute

sudo yum install ntp

Check whether ntpd starts automatically with the command

systemctl list-unit-files | grep ntpd.s

ntpd.service enabled

If ntpd is inactive (disabled) execute

systemctl start ntpd
systemctl enable ntpd

To check whether the ntp service has been added to the public zone in the firewall, you can use the command

sudo firewall-cmd --get-services | grep ntp

If not already added, then to allow UDP traffic from ntp execute

firewall-cmd --permanent --add-service=ntp
firewall-cmd --reload

success
success

Edit the file ntp.conf with server settings

vi /etc/ntp.conf

Find your time zone on the site www.ntppool.org

I found the zone Helsinki and I add the lines

server 0.fi.pool.ntp.org server 1.fi.pool.ntp.org server 2.fi.pool.ntp.org server 3.fi.pool.ntp.org

Now you need to restart ntpd

systemctl restart ntpd

You can check where the time comes from with the command

ntpq -p

remote refid st t when poll reach delay offset jitter ============================================================================== time.cloudflare 10.79.8.177 3 u 14 64 7 3.987 -0.366 0.016 37.228.129.2 193.66.253.94 2 u 16 64 7 5.301 -1.639 1.908 ivanova.ganneff 237.17.204.95 2 u 13 64 7 5.296 3.850 0.266 ntp23.kashra-se 192.168.100.15 2 u 12 64 5 32.935 -2.213 0.192

You can set the BIOS time according to the time you just received with the command

hwclock --systohc

Force the system to synchronize time with ntp

You can use the following command

ntpdate -u 0.fi.pool.ntp.org

Instead of 0.fi.pool.ntp.org install the server you need

Timezone

Find out the current time zone

timedatectl

Local time: Fri 2021-05-21 01:42:44 MDT Universal time: Fri 2021-05-21 07:42:44 UTC RTC time: Fri 2021-05-21 07:42:43 Time zone: America/Denver (MDT, -0600) NTP enabled: yes NTP synchronized: yes RTC in local TZ: no DST active: yes Last DST change: DST began at Sun 2021-03-14 01:59:59 MST Sun 2021-03-14 03:00:00 MDT Next DST change: DST ends (the clock jumps one hour backwards) at Sun 2021-11-07 01:59:59 MDT Sun 2021-11-07 01:00:00 MST

You can change the time zone with the set-timezone command

timedatectl set-timezone "Europe/Helsinki"

Check the result

timedatectl | grep "Time zone"

Time zone: Europe/Helsinki (EEST, +0300)

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