This package contains the Clock interface and implementations for generating UUID timestamps. UUID timestamps are measured in 100-nano second intervals since the Gregorian changeover epoch (00:00:00.00, 15 October 1582.) Due to several factors relating to time precision and time resolution on Windows ^tm and in Java ^tm in general; the Clock interface is introduced to allow different or custom strategies in timestamp generation. The IETF (Internet Engineering Task Force) specification details some of these approaches. For more information see the RFC 4122: A Universally Unique IDentifier (UUID) URN Namespace.

Two provided implementation are:

• SystemClockImpl - uses System.currentTimeMillis() and an artificial counter to allow up to 10,000 ticks per millisecond interval.
• ThreadClockImpl - time resolution on certain operating systems may not be 1-millisecond intervals. Windows ^tm according to some reports to have time resolution in the 1-ms to 54-ms range. Using a thread to provide a clock that increments it's counter at 10-ms intervals is one means of compensating for this. (Due to bug parade issue: 4500388 10-ms and not 1-ms intervals are used in this implementation.)