New Scientist Enigma 948 – Losing Time
by Colin Singleton
From Issue #2103, 11th October 1997
The church clock has developed a serious fault. The escapement keeps perfect time, but a small widget in the mechanism has become loose and drops out of place whenever the hands reach an exact hour. When the hour and minute hands next come together while the widget is misplaced, they rewind instantaneously to the previous exact hour (unless they are showing 12 o’clock) and the widget drops back into its correct position. The clock then continues running at the correct rate, but showing the wrong time.
If the hands come together with the widget correctly placed, nothing untoward happens.
The verger set the clock correctly at midnight on New Year’s Eve, and the fault became apparent over an hour later. If left unattended, when would the clock next be running normally and showing the correct (12 hour) time?