# User-defined clocks

The default clock used by pyglet uses the system clock to determine the time (i.e., `time.time()`). Separate clocks can be created, however, allowing you to use another time source. This can be useful for implementing a separate "game time" to the real-world time, or for synchronising to a network time source or a sound device.

Each of the clock functions are aliases for the methods on a global instance of clock.Clock. You can construct or subclass your own Clock, which can then maintain its own schedule and framerate calculation. See the class documentation for more details.