ntp server

http://www.pool.ntp.org/zone/cn

# yum install ntp

# vi /etc/ntp.conf

           server 1.cn.pool.ntp.org
	   server 0.asia.pool.ntp.org
	   server 2.asia.pool.ntp.org

/// /// firewall

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

/// /// systemctl

# systemctl start ntpd
# systemctl enable ntpd
# systemctl status ntpd

Reference : http://www.tecmint.com/install-ntp-server-in-centos/