Resetting the Clock after an Illegal Move
Authors: Masoud Sharafati - Hamidreza Jedidi

Introduction:
In a chess game, situations may arise where the arbiter needs to reset the clock. This could be due to a malfunctioning clock, incorrect initial settings, or the discovery of an illegal move.

In such cases, the arbiter must follow Article 7.1 of the FIDE Laws of Chess, restoring the position before the irregularity and using their best judgment to adjust the clock accordingly.
Formula for Calculating Time Used Until Move 30:

(Moves befor the illegal move / Total Move ) * Time used
Problem Statement:
In a standard game with 90 minutes of main time and a 30-second increment per move, the arbiter realizes at move 40 that Black’s move 31 was illegal. How should the arbiter reset the clocks?

Recalculating the New Time Controls:
White’s elapsed time: 80 minutes

Black’s elapsed time: 72 minutes

Formula for Calculating Time Used Until Move 30:
For White:

(30/40)*80=60 Minutes

For Black:

(30/40)*72=54 Minutes

Adjusting the Clocks After Recalculation:

Main Time + Extra Time = 105 Minutes So:
For White:
105-60=45 minutes
For Black:
105-54=51 minutes
Final Clock Settings:

White’s clock should be set to 45 minutes.

Black’s clock should be set to 51 minutes.