Oh this will be fun. Imo every country should be in the same time zone but I can imagine say Netherlands stay in summmer, Belgium in winter, Germany in summer, Poland in winter. Sounds fun!
I hope it's just a vague article and they mean member countries from the same timezone should decide together where they stay. Given there are 3 timezones in the EU it shouldn't be a big problem (or yes)
https://en.wikipedia.org/wiki/Central_European_Summer_Time#/...