Daylight Saving Time

As mentioned in my previous post, in the early hours of Sunday 27 October the clocks go back an hour throughout the European Union and daylight saving time comes to an end.

Although many Europeans will welcome the extra hour in bed on the night of 26/27 October, I suspect that a lot of people won’t like the darker evenings. In this post I’ll talk about daylight saving time (DST) : the practice of advancing the clock by an hour during the spring and summer months and why this is coming to an end in many countries.


The advent of DST

The first place in the world to practise DST was the town of Port Arthur, Ontario. In 1908, a local businessman, John Hewitson petitioned the town council to adjust the clocks one hour forward in the summer months so the locals could enjoy an extra hour of summer sun. The council agreed and the town turned its clocks ahead one hour from June to September.

DST became established in Europe and North America during the first world war. Two of the Central Powers (Germany and Austria-Hungary) adopted it in April 1916 followed by many European countries later that year. The US adopted it in 1918. The main justification for its use was that by having an extra hour of daylight in the evening, it reduced the need for energy in the stretched wartime economies.

Applying DST shifts the day.  People lose an hour of daylight in the morning and gain an hour of daylight in the evening. Advocates of DST believe that the extra hour of daylight in the evening can be put to good use – allowing people to do outdoor activities in the evening without as much need for artificial light. The hour of daylight lost in the early morning is of little importance, as it occurs before most people have started their daily activities. For example, on 20 June 2020, the Sun will rise in London at 4:43 AM and set at 9:21 PM (data from If the UK didn’t observe DST it would rise at 3:43 AM and set at 8:21 PM.

Supporters of DST claims it reduces energy usage for heating and lighting. Although this may have been true in the past, this benefit is now debatable. Modern light-bulbs are very energy efficient and,  in many Southern states of the US, DST causes energy consumption to rise because it is slightly warmer in the evening – increasing the energy used on air conditioning.


The Decline of DST

Despite some of its proposed advantages, only one billion people live in a place which observes DST. In the map below the countries are coloured as follows.

  • The areas shaded in blue observe Northern Hemisphere DST.
  • The areas in orange observe Southern Hemisphere DST.
  • The areas in dark grey have never observed DST.
  • The areas in light grey used to observe DST (or permanent daylight saving where the clocks are advanced by one hour all year) but no longer do so.


Image from Wikimedia commons.

One disadvantage of DST is that the twice yearly clock shifts are disruptive to sleep patterns and need to be manually applied in many clocks, watches and some central heating timers. On the day of the change there can be disturbance to plans and people can arrive an hour late or early for appointments.

Another issue is that countries which observe DST do not change their clocks at the same time. For example, New York, like most of the US, puts it clocks forward at 2 AM (local time) on the second Sunday in March and back at 2 AM (local time) on the first Sunday in November. Whereas London, like the rest of the EU, put its clock forward at 1 AM (UTC) on the last Sunday in March and back at 1 AM (UTC) on the last Sunday in October.  Therefore,  for most of the year New York is five hours behind London, but there are two periods when the time difference is four hours. This can cause confusion e.g. when people try to arrange a transatlantic phone call in either of these periods.

A further complexity is that the small number of countries in the Southern Hemisphere which still use DST put their clocks forward at the start of their spring (which corresponds to the Northern Hemisphere autumn) and back at the start of their autumn (which corresponds to the Northern Hemisphere spring). For example, on 5 April 2020 Chile puts its clock backward by one hour as it moves into winter time. It puts them forward by one hour on 6 September 2020 when it moves to summer time. For five months of the year Chile is on the same time as New York.  For roughly four and a half months Chile is two hours ahead and at other times one hour ahead. A recipe for confusion!

Data from

Recently, a number of countries have abolished the twice-yearly clock changes. In 2011 Russia switched to permanent summer time.

This was announced amid research claiming that changing the clocks  caused Russians ‘stress and illness’.  However, many Russians didn’t like very dark mornings in  winter  caused by having the clocks permanently advanced. For example, in Moscow, the sun didn’t rise until 9:57 AM on the date of the winter solstice. So, in 2014 Russia switched to permanent winter time to bring the civil time more in step with the solar time. Belarus, which has close political and economic ties with Russia also stopped the twice-yearly clock changes in 2011, but unlike Russia remains on permanent summer time (UTC+3).

Turkey (population 83 million) abolished DST in 2018 and remains on permanent summer time.

Other populous countries which have recently abolished DST include:

  • Argentina (population 45 million) in 2009.
  • China (population 1.44 billion) in 1991.
  • Iraq (population 39 million) in 2007.
  • South Korea (population 52 million) in 1988.
  • Uzbekistan (population 33 million) in 1991.

For more details see ( )

Future of DST in the EU

All countries in the EU put their clocks forward at 01:00 UTC on the last Sunday in March and back at 01:00 UTC on the last Sunday in October. However, this may change soon.

On March 26, 2019, the European Parliament voted in favour of backing the EU Committee draft directive to stop the one-hour clock change in the European Union.

Under this directive, each member state will have to decide until April 2020 to decide whether to remain permanently on summer time from March 2021 or to change their clocks back one final time in October 2021 and remain permanently on ‘winter time’.

However the  abolition of DST is opposed by many in the Republic of Ireland and the Irish government may well lobby other EU nations to reject the change. The Irish objection is because the UK (which includes Northern Ireland) should have left the EU by 2021 and has no plans to abolish the twice yearly clock changes. This would mean that, regardless of whether Ireland opted to remain on permanent winter time or permanent summer time, Northern Ireland and the Republic of Ireland would be on different time zones for approximately half the year. To many in Ireland this is unacceptable.

The Future of DST in the USA.

At present the US has no plan to abolish DST. Although individual states are allowed to opt out and remain on permanent winter time. At the moment, Hawaii and Arizona are the only states which do so.  Interestingly, states are not permitted to remain on permanent year-round summer time. In 2014 a poll of around 1000 American adults found that only a minority (33%) were in favour of the clock changes, 48% were against and the remainder unsure.

However, at the moment, there is no strong nationwide push to abolish DST


DST in the Future

DST is falling out of use and now out of the 7.8 billion people in the world only one billion live in area where it is observed. If the EU does abolish DST in 2021, this figure will reduce to half a billion. I think that it is very likely that in the next twenty years DST will fall into disuse throughout the world. Perhaps, in fifty years time, people will look back on DST as an arcane activity practiced in the twentieth and early twenty-first century.



15 thoughts on “Daylight Saving Time”

  1. I was really annoyed by DST – even though I live in Arizona, for a long time I worked in an industry where we were governed by the home office that DID observe DST. SO my shift would change even though the clocks didn’t. My current company is far more reasonable and I’m happier. I wonder why no one is allowed to stay on summer time?

    I wanted to share something with you though. It’s a fantastic science-rich blog that is presented by the people at Concordia Research Station in Antarctica. I am currently their only follower but their content is fantastic. So here is the link in case it’s of interest to you. I share their posts on my blog to try and increase their reach. They post about quite a few different topics.


  2. Excellent post! Thank you for liking a figment of my thought! I write primarily on metaphysics, yet adore all scientifically-inclined minds in all due intellectual humility of the apopathic unknown. In times of Plato, sciences were accentuated primarily, and to dwell into any form of theology, one had to prove a point with strenous effort to support his thesis, eliminating blind faith – as in the times of Hindi philosophers, a true sabre-duel symposia of great minds. I will gladly read your posts, I can see that you are a great educator and that commands respect! Believe it or not, Carl Sagan loved stars the most, and I can swear on my head that post-mortem he joined the great procession of stars above, it seems we gravitate towards what love most. Giordano Bruno wrote that there is an “infinite number of worlds”, seems there is a place for everyone. Best wishes – from a friend.

    Liked by 1 person

  3. Unfortunately our government here in BC decided that the (loudly declared) wishes of our province, (BC) and the Yukon, which is in the same time zone as us, can’t have our cake and eat it too, because Washington can’t get it’s shit together in time. I HATE politics. 😦

    Liked by 1 person

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