Network Time Protocol (NTP) is a protocol that is used to synchronise computer clock times in a network of computers. On Clusters or realtime/scientific computing or Parallel processing computing environment must have proper time across all the nodes. We use NTP to sync time. NTP uses Coordinated Universal Time (UTC) to synchronise computer clock times to a millisecond, and sometimes to a fraction of a millisecond.
SNTP is a reduced version of the NTP protocol that can be used to replace TIME clients. NTP is implemented via UDP over port 123, and can operate in broadcast and multicast modes, or by direct queries.
There are free NTP servers available for every region. Below is the available NTP servers from the pool.ntp.org project for India and Asia region.

server 2.in.pool.ntp.org
server 0.asia.pool.ntp.org
server 3.asia.pool.ntp.org
How to Configure NTP on a linux (CentOS/Redhat.
1. We have to add the NTP server information in, /etc/ntp.conf, You can use any of your favourite text editors, example Vi, emac etc.
# vi /etc/ntp.conf

server 2.in.pool.ntp.org
server 0.asia.pool.ntp.org
server 3.asia.pool.ntp.org

2. Restart the ntpd daemon.
#/etc/init.d/ntpd restart