Daylight saving time explained

Clarifying why we make our lives harder by resetting our clocks biannually

science 31.10.23   •   8 min
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On 29th October this year, we set our clocks back by one hour in Britain at 2 am. Internet-connected clocks, such as the ones on our phones, handled this just fine; but their analog counterparts—on our ovens, boilers and building towers—promptly ended up wrong by one hour. This little dance marked the end of Daylight Saving Time, known simply as “daylight saving” or officially “British Summer Time”. In Winter we return to the ‘correct’ time zone for this country, corresponding to the former Greenwich Mean Time, now called Universal Co-ordinated Time and shortened to UTC (due to the French)1.

Many of us find it hard to understand why daylight saving is needed in the first place, and how and why it works. This essay is an attempt at offering a self-contained clarification to all these questions.

Let us get some shortcuts in place to understand this game of clock-setting. First, keep in mind that daylight saving does not start in October, it ends in October. Trying to understand why we alter our clocks by examining the winter months will therefore make it harder to make sense of it all. Therefore, lesson number one, the time it is in winter—starting around the end of October—is the correct time. This will be our reference point.

Sunrise… sunset…

These words from the brilliant play Fiddler on the roof echoes in my mind whenever I think of daylight saving. On a normal day—which is pretty much every day the closer you head towards the equator—the sun rises at 6 am and sets at 6 pm.

For example, on 1 June 2024, the time of sunrise in India is set at 6:00 am and that of sunset at 7:30 pm. If you go closer to the equator, it gets closer to the 6 am – 6 pm bracket. For example on the same day in Equador, which lies exactly on the equator, the sunrise is at 6:09 am and the sunset is at 6:15 pm. As India is a bit further away from the equator than Equador there is a bit of a time shift. However, the difference of 45 min or so does not matter too much in practice.

The UK is much further away from the Equator and much closer to the North Pole, so the time shift is much more pronounced. On 1 June 2024 in the UK the sunrise time is set at 4:49 am and the sunset at 9:09 pm respectively. The time shift is now much more pronounced. Roughly, this shift is about 254 min in total compared to Equador and about 209 min compared to India. With the sun rising earlier and setting later, the UK is now left with over 200 min of extra daylight.

Living on borrowed time

The question now is what you do with all that extra sunny time. Most people are in bed till 6 am, and at work between 9 am and 5 pm, and are out shopping or dining till, say, 9 pm and then they go home and do some chores and watch the tele and go to bed by 10 pm or 11 pm. This means they use up electricity and artificial light for about two hours after sunset and, in the mornings, they are asleep for about two hours when the sun is already up and shining. In other words, you have a couple of hours of wasted daylight in the morning that you could instead use in the evening.

Daylight saving is a policy matter, not a scientific concern.

A better way to think of daylight saving time then is to think of it as “borrowing” time from one part of the day to another. Specifically, daylight saving is about borrowing time from the mornings and handing it to the evenings. Those two hours of wasted daylight when you were asleep till 6 am can be ‘saved’ if we move the clocks ahead i.e. you turn the 5 am sunrise into a 6 am sunrise so you get up without losing daylight, and then you turn the 9 am sunset into a 10 pm sunset so you get an extra hour of sun during which household energy consumption drops.

This is not just about lights; you also do not have to turn on your heater throughout the day because you have no need for either artificual light or artificial warmth.

From Ben Franklin to the First World War

The inimitable Benjamin Franklin was the first person to speak of an idea resembling daylight saving. He reasoned that doing so would mean we save on candles. Back then nobody bothered: how expensive could candles really get? In his famous quote, “early to bed and early to rise makes a man healthy, wealthy, and wise”, the claim to get ‘wealthy’ supposedly comes from the savings made on burning candles by arising early in the months when the sun rises early2.

In 1895 the New Zealander George Hudson, a hobbyist collector of insects, presented the idea of daylight saving because he wanted more daytime hours to collect insects. Nobody took the idea to implementation back then.

By the mid-1910s the First World War was in full swing and countries really started to feel the pinch. Sure, we had moved to modern electric grids just then (1880s–1910s) and candles were not as common as they were before but there were costs associated with lighting up homes anyway. They had simply moved from candles to electric grids, and Canada first moved, in 1908, to implement daylight saving. Britain and Germany followed in 1916 and the US in 1918.

daylight saving war propaganda poster from the US

The US used war propaganda to coax people into implementing daylight saving, reasoning that it would save the country money spent on coal that it could instead use on its war efforts. Japan made no such attempts and so its people shot down the idea of daylight saving when the government proposed it. This is why, despite being at the same distance from the equator as the US, Japan does not implement daylight saving. Further, regardless of the war, countries closer to the equator saw no need to switch to daylight saving while those further away needed more extreme measures3 such as implementing permanent daylight saving all year-round (e.g. Russia and Belarus).

Pros and cons

Daylight saving is a policy matter, not a scientific concern. While it is possible that syncing our waking hours with the sun might reduce energy consumption, the argument may no longer be valid in a society that produces self-sustainable, non-renewable energy at low or near-zero costs.

Some religions oppose daylight saving claiming it strains their beliefs. Muslims fasting during Ramadaan is a common, recurring example in countries around the globe. Morocco, for instance, uses daylight saving throughout the year but abandons it temporarily during the Ramadan month to help in fasting by reducing daylight hours. Lebanon on the other hand saw communal divide and confusion earlier this year when a last-minute decision to delay clock resets in favour of Muslims saw the Christian half of the country on a different time zone as a mark of opposition.

The exact benefits to energy consumption remain to be seen, so also the effects of daylight saving on health. Winston Churchill famously claimed daylight saving would give individuals more time to focus on their health with opportunities for walks and outdoor exercises. Funnily enough, among all the arguments it may be that Churchill hit the nail closest on the head: while energy savings are not a universally proven rule (savings were observed in Norway and Sweden but not considerably in parts of the US) most countries that still implement daylight saving do so because the extra evening daylight allows people to go out after work hours. Britain does it for this reason as well.

Saving daylight permanently

All said and done, reverting from daylight saving is not a popular move. A 2018 poll suggested that 80% of Europeans did not support daylight saving. The quicker darkening of day after daylight saving is reversed is also seen as a menace for traffic, which is why many traffic authorities oppose daylight saving. Along similar lines, turning back clocks to the ‘proper’ time in October increases energy consumption anyway as the days get darker sooner. Would it not make sense then to continue in daylight saving time and give up on the ‘proper’ time altogether?

That is to say, if in the winter the day gets darker sooner, why does Britain not continue to implement daylight saving time in winter too? After all it is better that the sun sets at 5 pm than 4 pm. In fact this is precisely what some countries, like Singapore and Iceland, have done and it is known as ‘permanent daylight saving’. Clocks are moved once for good rather than biannually. Here in Britain, a little over 50% of people seem to support the idea of permanent daylight saving but change does not seem to be on the horizon. After all the EU voted to scrap daylight saving back in 2019 but has still not put that law in place.

There is no question then that daylight saving time is a good idea in terms of maximising the available daylight. What it has done, inadvertently, is make us all realise that reverting to our normal times means losing out on daylight similarly. Until countries sort this out at a policy level, we will have to stick to the old American mnemonic of moving our clocks: Spring forward and Fall back.

  1. The Brits wanted to call it Co-ordinated Universal Time or CUT while the French wanted to call it Temps Universel Co-ordonné or TUC so the International Astronomical Union decided a middle path and abbreviated it to UTC. 

  2. I would take this claim with a grain of salt. The attribution of this quote is itself in question at times, but Ben Franklin’s French connection is real: he did publish an essay in Paris suggesting that the French should arise earlier in the day to save daylight hours. 

  3. Antarctic research stations often switch by two hours rather than one. 

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