@MarciKS It has to do with the EU. Previously each member state could decide when they would implement DST. To avoid confusion with member countries going on to and off DST on different dates the EU decided that all member states would use the same date. The UK have now left the EU but still use the same dates.
However just to confuse things there is now a proposal to do away with DST in the EU and let each member state decide individually which time they will use as standard time DST or winter time