A refund rather than a fixed bonus
In a refund-style Bronstein clock, the displayed time counts down during your turn. When you complete the move and press the clock, it returns whichever is smaller: the time you used or the configured delay. That means your settled remaining time cannot increase beyond the amount at the beginning of the turn.
A five-second delay is therefore not a five-second increment. If you use only two seconds, you get two seconds back. The other three seconds disappear rather than becoming extra time you can spend later.
Two moves with a five-second delay
Suppose your turn starts with one minute remaining. With a five-second Bronstein allowance, a three-second move temporarily takes the display to 0:57. Pressing the clock returns those three seconds, leaving 1:00.
If the move takes eight seconds, the display falls to 0:52. Pressing the clock returns five seconds, leaving 0:57. You have spent three seconds of main time overall. The refund is capped at five seconds even if the move takes much longer.
Refund = the smaller of time spent and selected delay
After a clock press before flag fall = starting time − max(0, time spent − delay)
These are completed-turn examples made with enough time left to press before expiration. A refund is not a promise that you can let the display reach zero and recover afterward.
What happens to unused delay?
Unused delay does not carry over. Ten quick moves made within a five-second allowance leave the main time unchanged, rather than adding fifty seconds. On every new turn, you have a fresh delay allowance; you do not keep a balance of unused seconds from earlier moves.
That is the main difference from Fischer increment. Fischer awards the full bonus after a completed move and can increase the clock. Bronstein only refunds time already used, up to the limit.
Bronstein versus US Delay
US Delay holds the main clock at the start of the turn while a separate delay interval passes. Bronstein’s refund-style display begins falling immediately and returns qualifying seconds on the press. For completed turns with enough time remaining, the settled main-time calculation is the same.
For a three-second move and five-second delay, both leave the main budget unchanged. For an eight-second move, both cost three seconds. The player sees a different display during the turn, even though those after-move figures match.
Near flag fall, implementation details matter. Chess Clock’s Bronstein mode counts the displayed main time down and checks expiration before issuing a refund. Its US Delay mode protects the delay interval before consuming main time. Do not assume that a pending Bronstein refund extends an already exhausted clock.
How to choose Bronstein in the app
- Select an available starting-time preset.
- Choose Bronstein in the timing selector.
- Set an available common delay value.
- Review the summary with your opponent and use Start.
- After each move, tap your active clock before the countdown expires.
Bronstein and common delay values are free. The optional one-time Pro unlock adds custom starting times, custom delay values and advanced setup. It is not required merely to select this timing mode.
Choose the mode deliberately
If you prefer seeing your main time stay still during the initial allowance, consider US Delay. If you prefer the refund display, choose Bronstein with an understanding of the app’s flag-fall behavior. If you want fast moves to build time, choose Fischer.
The complete timing-system comparison puts the three modes side by side. Pause/resume and history are included regardless of the timing system; history records the time control and result, not chess move notation.
Product features: Chess Clock on the App Store. Standard timing modes are free; Pro unlocks custom values.