Alternatively referred to as a GUID (globally unique identifier), UUID is short for universally unique identifier. It is a 128-bit unique identification value. UUIDs are used in the Apollo Network Computing System, OSF (Open Software Foundation), DCE (Distributed Computing Environment), and Microsoft Windows, and is fully defined in RFC 4122. Below is an example of a UUID.
In the example above, the timestamp of Monday, July 25, 2005 3:59:05 A.M. MDT is encoded into the UUID.