This coming Sunday sees the clocks throughout most of Europe change to wintertime by going back an hour. Daylight Saving Time was originally proposed in 1895 by George Vernon Hudson, who was a British-born New Zealand entomologist and astronomer.

At the beginning of 2019, member states of the EU unanimously decided that each country should choose which side of the timeline they should permanently stick with. Spain for instance changed time zones back in 1940 and is considered to be in the wrong time zone, and should be in the same as its neighbour Portugal, Ireland and the UK. The decision is supposed to be taken in March or October 2021 and then adhered to.
Europe is spread across three time zones, and nearly every country in Europe observes daylight saving time. The UK, Ireland and Portugal are all on Greenwich Mean Time (or UTC), while 17 countries in western and central Europe are on Central European Time (UTC+1). Eastern Europe is on the equally ingenious named Eastern European Time (UTC+2).
Now that the UK has left the European Union, it is free to continue using daylight saving time if it so chooses although it is likely that they will follow the rest of Europe. If they do not, it could cause problems, where Northern Ireland and the Republic of Ireland could end up in different time zones, despite being right next to each other.
Back in December 2011, the tiny South Pacific nations of Samoa and Tokelau, made the momentous decision to move themselves forward across the international dateline, effectively jumping forward an entire day and erasing December 30, 2011 from its calendar altogether.

Daylight Saving Time is not used near the equator, as sunrise and sunset times do not vary enough to rationalize it. Places like Australia observe it for some regions, and almost nowhere in Asia and Africa utilise it.

Having said all this – with the COVID 19 situation remaining uncertain, I wonder if this action will be delayed, as the planned consultative phases have yet to be undertaken.