British Double Summer Time: The Wartime Clocks
In the Second World War the UK went beyond summer time and used British Double Summer Time, two hours ahead of GMT.
What it was
From 1941 to 1945, and again in 1947, the UK used British Double Summer Time, BDST, which was GMT+2 in summer. In winter the clocks stayed at GMT+1 during the war years, called British Summer Time all year, instead of returning to GMT.
Why
The extra daylight in the evening saved fuel and let factories and farms work longer, while the black-out rules made the darker mornings acceptable. After the war the UK returned to the pattern of GMT in winter and BST in summer, with a later experiment in all-year BST from 1968 to 1971.
Frequently asked questions
When did the UK use double summer time?
In the summers of 1941 to 1945 and in 1947.
Clock change guides
- What Is Daylight Saving Time (DST)? A Plain-English GuideWhat daylight saving time is, how it works in the UK, Europe and the US, why it exists, its history, who uses it and the argument over scrapping it.
- Why Do the Clocks Go Back in October? The Real ReasonThe clocks go back in autumn to return the UK to GMT, so winter mornings are lighter. The history, the rule, what time it happens and what changes for you.
- When Do the Clocks Go Forward Again After Going Back?When the UK clocks go forward again after the autumn change, how long the UK stays on GMT, when evenings get lighter and how to remember to reset your clocks.