Time stamps in MTConnect are based on Universal Time Coordinated (UTC). Also known as Greenwich Mean Time (GMT). Or ZULU time by the military. This allows factories in different parts of the world to be monitored and used in the same reports without error caused by Time Zone difference.
Getting all your equipment clocks to be correct can sometimes be difficult. If the controller is based on WINDOWS, you can use time servers to synchronize them.
MTConnect Agents have the ability to ignore the time stamps from the equipment (Adapters) and use the servers local clock to replace any errors thus keeping all the equipment in synch. By putting all your Agents on the same server, you can easily control your time stamp synching and allow easier maintenance of settings. This is desirable in large or mixed device type implementations. But it is strictly an implementation preference.