Little-known 4-minute rule explained as clocks set to spring forward

Many Britons eagerly anticipate the end of dark mornings and evenings, which typically signals the arrival of milder weather. Whilst the darker, cold nights might suit the winter festive period, once they’ve passed, the countdown begins for spring and summer, bringing extended days and, with any luck, sunshine.

The most significant shift occurs when the clocks change, moving from Greenwich Mean Time (GMT) to British Summer Time. This year, it takes place on March 29, with clocks staying that way until October 25 when they’ll revert to GMT. However, there’s also a four-minute rule that will see evenings become lighter throughout March. This means that by the end of the month, it won’t simply be the additional hour of daylight that people will be enjoying.

According to timeanddate.com, you gain just under four minutes of extra daylight each day during March. This accumulates to a substantial difference by the month’s end.

Whilst times will differ slightly depending on your location, in London on March 1, the sun rises at 6.45am and sets at 5.40pm, providing 10 hours, 54 minutes and 53 seconds of daylight. Yet on March 28 – the day before British Summertime commences – the sun will rise at 5.45am and set at 6.26pm, meaning there’s daylight for 12 hours, 41 minutes and 50 seconds.

By March 31, accounting for the clocks going forward, the sun will be rising at 6.38am and setting at 7.32pm. This means there are 12 hours, 53 minutes and 41 seconds of daylight.

Just one month afterwards, by April 30, there will be daylight from 5.34am until 8.22pm, and then on 31st May this will have stretched further with sunrise at 4.49am and sunset not occurring until 9.07pm.

Time and Date states: The June solstice (summer solstice) in London is at 09:24 on Sunday, 21 June, 2026.” On this date the sun will rise at 4.43am and set at 9.21pm giving 16 hours, 38 minutes and 22 seconds of daylight.

It adds: “In terms of daylight, this day is 8 hours, 49 minutes longer than the December solstice. In most locations north of the equator, the longest day of the year is around this date. The earliest sunrise is on 17 June. The latest sunset is on 24 June or 25 June.”

Will I gain or lose sleep with British Summer Time?

The Royal Museums Greenwich has clarified why the clocks change and whether we lose or gain sleep when BST begins. It stated: “Unfortunately, the clocks moving forward means that we lose an hour in bed.

“An easy way to remember which way the clocks change at which time of year is to remember that the clocks ‘spring forward’ in spring, and ‘fall back’ in autumn.”

It explained the clock change was down to a campaign more than 100 years ago. It said: “The clocks go forward for the summer because of a campaign at the beginning of the 20th century to change the clocks during the summer months, in a practice known as British Summer Time.

The original campaign attempted to argue that by changing the clocks during the summer people in the northern hemisphere could make more use of the earlier daylight hours. William Willett – an early promoter of British Summer Time and great-great-grandfather of Coldplay singer Chris Martin – published a pamphlet in 1907 titled ‘The Waste of Daylight’, which suggested changing the clocks in the spring and putting them back in the autumn.

“However, Willett’s proposal was complicated, involving advancing the clocks by 80 minutes in four separate moves of 20 minutes each. Willett died in 1915. A year later Parliament passed the Summer Time Act, which established the practice of putting the clocks an hour forward during the summer.”

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