When does time change?

When does time change? Why does time change? How does time change?

When does time change in 2020?

Alarm clock. Picture by Lukas Blazek, available at https://commons.wikimedia.org/wiki/File:Alarm_clock_friends_situation_with_hand_(Unsplash).jpg, license - CC0 1.0 Universal (CC0 1.0) Public Domain Dedication.

Chance is, if you live in Russia, China, Indonesia, Thailand or Japan, the question on when does time change appears puzzling – perhaps something from astronomy. To us, people living in most of the US, Europe, parts of Australia and New Zealand, this is a peculiar habit that all of us have to go through each half a year. Hours on all clocks shift one hour forward or backward. So, when does time change? And why?

When does time change in 2020?

In Europe, time change is usually called switching to summer time or winter time. In the US, this is usually called daylight saving. It happens with a slight delay: the US shifts clocks first, and two weeks later Europe does it. Even before the two, time change takes place in Australia and New Zealand.

Summer timeWinter time
Australia First October Sunday First March Sunday
New Zealand First October Sunday First March Sunday
USA*Second March Sunday Second October Sunday
UKLast March Sunday at 1am UTCLast October Sunday at 1am UTC
Europe** Last March Sunday at 1am CET (UTC+1) Last October Sunday at 1 am CET (UTC+1)

*Except Arizona and Hawaii, which do not have time change.
**Referring to CET (UTC+1) Europe.

How does time change?

Today, on 29th of March 2020, Europeans just woke up with their smartphones, laptops and computers already having adapted to the time change to summer time. The simple electric alarm clocks and most hand watches do not detect time change, and stay in winter time. So, most of us woke with a set of clocks at home, showing different hours.

My bed alarm clock shows 7am at the moment of writing this text, and so does my Casio hand watch. My computer and smartphone show 8am. This means that I need to manually change the bed alarm clock and my hand watch to 8am.

If you were to stay awake at night to see what happens to time change on automatic devices such as computers, laptops and smartphones, you would wait today at 1:59am until the number of seconds shows :59, and after which the clock suddenly jumps to 3:00am, skipping 2am entirely.

In October, this entire ritual would be reversed.

Why does time change?

The core idea is to save on daylight. This might be more understandable to the Russians reading this blog – much less so to South East Asians or the Chinese. Let me explain first one thing then: the more to the north or south you live (farther from the equator), the larger the difference between day and night. You heard that on the poles there is a night that lasts 6 months and day that lasts six months? Well, you don’t have to on the poles to experience this kind of thing.

National Geographic’s documentary on YouTube about the history of Daylight Saving. Very informative!

Here in northern Poland, around 17th of June, our sunrise will take place at 4:20am, and sunset at 9:17pm. And at about the end of December, sunrise will occur at 8:02am, and sunset at 3:39pm already. The more to the north, the sharper the difference. In March and October, day and night time equalise, a moment of year called the equinox.

Modern daylight saving system was proposed by George Hudson, a New Zealand entomologist, in 1895. The reason was personal: working on shifts, Hudson used his spare time to collect insects, and varying daylight duration as months pass interfered with this hobby.

At the same time, English builder William Willet, a golfer, independently coined the idea in 1905, to observe how many in London slept through summer day. He lobbied for his proposal until death in 1915, in the United Kingdom.

First city to enact the system was Port Arthur in Canada in 1908. Country-wide, first the German Empire and Austria-Hungary enacted daylight change on 30th of April 1916, and soon Britain and its European allies, and many neutral states, adopted the change.


In modern era, the daylight saving habit proves highly controversial and there are multiple debates on whether it should be abolished.

“But increasingly, many people in the US want to be done with this clock-changing ritual for good.” – Business Insider


As for Europe?

“The European parliament has voted to scrap the twice-a-year custom of changing the clocks by an hour in spring and autumn by 2021, leaving only national governments to now give their assent.” – The Guardian


The discussion went on far enough for the European Union to vote for a complete removal of this habit. When exactly, that remains an open question. As of today, the ritual stands.

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