Activate() is called whenever the move changes from black to white to black. When white completes a move, he presses the button, and his clock stops, but black's clock starts ticking, carrying on from where it left off.

In tournament chess, you have, for instance, 2 hours to make the first 30 moves. The clock for white will show the total time used by white to make his moves so far. If this exceeds 02:00:00 before move 30, he has lost the game.

The idea with using this app as a chess clock, is that once you have set up the buttons for White and Black, you save these into a file, say chessclock.ini. Now, every time you need a chess clock for a match, open chessclock.ini - save as something else if you want, and the times are reset to 00:00:00.

Hope this helps