How to Synchronize Time and Timezone on CentOS 7 / RHEL 7 / SL 7 / OL 7. Time synchronization is the most vital part of any Linux distros. The configuration of time sync is straight forward using NTP (Network Time Protocol). It includes some couple of commands that works fine with the time synchronization. Keeping different clocks running into a same severs is a quite interesting task to keep running your system time up to date. When any user login to your system so it is so important task to note the user login time according to the local time of that system time zone. Most of the services are running in different time zones so it is vital need to run the system with accurate time.

Step-1 : Check the different available time zones

$ sudo timedatectl list-timezones

Step-2 : Set your Time Zone from different timezone

$ sudo timedatectl Asia/Kolkata

Step-3 : Sync time using NTP daemons

There are two types of NTP daemons including chronyd and ntpd. You should select and use only one to avoid running two NTP daemons at a same time on same machine this cause ntp incompatibility and instability using two NTP daemons at same time.
This tutorial includes two NTP daemons you should select any one:

1. Sync time using chronyd (Suitable for virtual system)
2. Sync time using ntpd (Suitable for networking system)

1. Sync time using chronyd

Install the chronyd package

$ sudo yum install chrony

Start the chronyd services

$ sudo systemctl start chrnoyd

Edit the configuration file

$ sudo vi /etc/chrony.conf

Add these lines

For CentOS

server 0.centos.pool.ntp.org iburst
server 1.centos.pool.ntp.org iburst
server 2.centos.pool.ntp.org iburst
server 3.centos.pool.ntp.org iburst

For RHEL

server 0.rhel.pool.ntp.org iburst
server 1.rhel.pool.ntp.org iburst
server 2.rhel.pool.ntp.org iburst
server 3.rhel.pool.ntp.org iburst

After adding these lines simply save and exit.
Restart the services to make changes in effect.

$ sudo systemctl restart chrnoyd

Enable this services to run at every boot.

$ sudo systemctl enable chrnoyd

OR

$ sudo yum install ntp

$ sudo systemctl start ntpd

$ sudo vi /etc/ntp.conf

server 0.centos.pool.ntp.org iburst
server 1.centos.pool.ntp.org iburst
server 2.centos.pool.ntp.org iburst
server 3.centos.pool.ntp.org iburst

server 0.rhel.pool.ntp.org iburst
server 1.rhel.pool.ntp.org iburst
server 2.rhel.pool.ntp.org iburst
server 3.rhel.pool.ntp.org iburst

$ sudo systemctl restart ntpd

$ sudo systemctl enable ntpd