Fischer's Chess Clock Hands Time Back After the Move, Not Before

A Fischer increment adds a fixed amount of time to a player’s clock after that player completes a move. It comes from US patent 4,884,255, “Digital chess clock,” filed by Robert J. Fischer on August 5, 1988 and granted on November 28, 1989. The description says “a predetermined interval of time will be added to the time remaining from that player’s initial time period.”

Run the arithmetic on a game with 15 minutes and a 10-second increment. A player who takes exactly 10 seconds per move still has 15:00 after 40 moves. A player who averages 5 seconds per move ends with 15:00 plus 40 × 5 seconds, or 18:20. A player who averages 20 seconds ends with 15:00 minus 400 seconds, or 8:20. The credit arrives only after each move is made, so it cannot be drawn on before the thinking is done.

Snooze runs in the other order. Each press spends nine minutes of morning, the iPhone’s default interval, and nothing is credited back for anything. Snooze is also the preset that wins when no one chooses.

The comparison has a limit. An increment does not cure slowness, and a player who burns more than the increment on every move still runs out of time. It only changes when time arrives.

An alarm built like Fischer’s clock would pay out its extra minutes after you were standing up.