This class is designed for in game timers. The time is based on milliseconds, and so works in real time.
With this you can get the percentage complete, a value from 0.0 to 1.0, which allows you to animate graphics over time. They are also re-usable, with you being able to reset or invert a time on the fly.
You create a new Timer, giving it a duration which it will last for. You can then check if it has passed the duration by calling 'isExpired'.