Originally posted by XanthosNZ
Starts when the tournament starts (after the timeout period of course). So yes you can timeout an opponent who never made a move in a tournament (or clan or league or siege) game.
When I started playing the new round of the From Tournament, I noticed that I allegedly still had the full timeout period (plus timebank) for my first move, although the game had been up for some hours. So either the clock doesn't start right away, or the time which is shown is not correct.