The Stopwatch tool lets you keep track of time. Touching the Start button starts the timer. While running, the Lap button records the current time in the window below and resets the timer to zero, but keeps counting. To clear the stopwatch, touch the Reset button while the stopwatch is stopped.
The stopwatch remembers the time and whether or not it is running, so it is safe to exit the application without losing your time. When you return, the time will be correctly updated and the stopwatch will resume its previous state of operation.