This is part of my complete guide to Setting up a CentOS Digital Ocean droplet with Nginx for beginners.

If you just need the commands, here they are. Read on for an explanation of what is happening.

sudo timedatectl list-timezones #copy your zone  
sudo timedatectl set-timezone region/timezone  
sudo yum install ntp  
sudo systemctl start ntpd  
sudo systemctl enable ntpd  

I am not going to bother repeating the excellent explanation of these commands from their source guide. If you are interested, check it out.