Computers, like any digital device, have clocks in them. Aside from telling users the time, they also provide a sequencing mechanism for internal core functions and digital circuitry. However, sometimes these clocks malfunction. It might be because of a bad CMOS battery or a timezone mix-up. Fortunately, CentOS, or any Linux box for that matter, have a tool that synchronizes its clocks with central servers.
The Network Time Protocol (NTP) is such a tool. It functions as an initial configuration setter and auto updater for Linux or CentOS boxes.