As I understood it, the EU will stop messing around with changing the clocks twice a year but it will be up to each member state to decide whether their country stays in summer or winter time.
Under the new legislation, governments opting to make summer time permanent would adjust their clocks for the last time on the last Sunday in March 2021.
For those choosing permanent standard time - also called winter time - the final clock change would be on the last Sunday of October 2021.