https://www.bbc.co.uk/news/world-europe-45366390
There are three time zones in use across the EU, reflecting the needs of countries base on both their latitudeand longitude. Daylight saving time in te UK means lighter mornings in the Winter, and lighter evenings in the summer.
Other countries do the same thing for similar reasons.
The EU is proposing to abolish this clock changes giving a unified European time. However these are only proposals ant the consultation stage.