Absolute Timing (Sudden Death) is the time system where
- one gets an amount of time (say, 75 minutes)
- and time used for each move is deducted.
|----------| time before
|----| time for one move
|-----| time after
The advantage of this system is that no fancy clock is needed and that the game is limited to a fixed time.
The inconvenience is that it animates some people to play junk moves instead to resigning, in the hope that their opponent runs out of time (Stubborn Play, Continue While Dozens of Points Behind).
This system is not very popular on Go servers.
# Time (mins) Used ------------------------- 1 75:00 1:00 2 74:00 2:00 3 72:00 22:00 4 50:00 30:00 5 20:00 10:00 6 10:00 9:00 7 1:00 1:00 8 0:00 lost
 Richard Hunter: I like to play 15-minute sudden death on KGS. I have only had one bad experience and the problem was fixed by wms, who responds very well to requests. I complained about an opponent who tried to run me out of time by playing every sente move, then every dame point, and finally all over his own territory. Each reply or pass took me a minimum of one second. wms fixed this by making a pass reset your clock back up to 15 seconds, if you had that much time before passing. This gives you enough time to decide that a move does not threaten anything and you can safely pass. Only further moves cause time to be deducted.