Rule 21 – Hours of Darkness (HOD). The HOD shall be:
From 21.30hrs day of liberation until 04.45hrs next day for races taking place in May and July.From 22.00hrs day of liberation until 04.30hrs next day for races marked in June.
From 20.00hrs day of liberation until 06.15hrs next day for races taking place in September.
Lerwick Hours of Darkness From 21:30hrs trough to 04:45hrs
Early times may be viewed here