Fischer increment, Bronstein delay, US delay and hourglass clocks sound similar, but change how much time each player can use. Here is what each one means and when to use it.
| Mode | What happens | Can time accumulate? |
|---|---|---|
| Fischer increment | The specified number of seconds is added after a completed move. | Yes, unused bonus can accumulate. |
| US simple delay | A short grace period runs before a player's main time starts decreasing. | No; the delay resets each move. |
| Bronstein delay | Time spent on a move is refunded up to the delay value after the move. | No; refunds do not exceed actual time used. |
| Hourglass | One player's used time is added to the opponent's time. | Time moves between the two players. |
With a 5-minute game plus a 3-second increment, each player starts at five minutes and receives three seconds once they finish each move. A player who moves quickly can build up some extra time.
Use it when you want players to retain a little thinking time even late in the game.
With a 5-second US delay, the first five seconds of each move do not reduce the main clock. If a player thinks for seven seconds, only the final two seconds are deducted.
The delay is refreshed on every move; unused delay is not banked.
With a 5-second Bronstein delay, the clock tracks elapsed time and refunds up to five seconds at move completion. Spend three seconds and three are refunded; spend eight and five are refunded.
It does not award more time than the player spent on that move.
In hourglass mode, as one player's clock runs down the other player's clock gains the same duration. This creates a different type of time pressure because the clocks are directly linked.
It is useful for casual and experimental matches, not necessarily supported in every tournament.
Keyboard shortcuts: Space to press the clock, P to pause, Z to undo, and R to reset. Stage bonuses and uneven player starting times are available.
For a familiar casual game, start with five minutes and a small Fischer increment. To ensure that a short move takes no main time, consider US delay. Bronstein delay refunds time actually used up to a cap. Hourglass gives both players a shared pool of time that shifts throughout the game.
For organized competitions, always check the event's official rules and device requirements. Clock84 is a browser-based tool, not a certified tournament clock.
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