I don't see how this is different from what the United States federal government attempted with the Metric system back in the 1970s. Granted, the effort failed, but more due to cultural inertia than due to any resistance from the states, as far as I'm aware of.

It makes sense for a trade bloc to maintain the same changeover dates for timezones, while leaving the timezone offsets up to each country, because this makes timezone conversions predictable, which I imagine is handy whenever cross-border scheduling is needed.

You could call it micromanagement, but do remember that the member states vote over these things, so it's not like they didn't have a chance to reject it.

One thing to remember about the EU is that anything that can be implemented at a higher administrative level is something that you, the government of the member state, are no longer responsible for. If you need to implement an unpopular but necessary measure, all you have to do is get the bigger member states to go along with it, and presto, you can wash your hands of it, with responsibility diluted across the Brussels bureaucracy and no one in particular to blame.