Daylight Savings Time

Yes, Jeff, we got caught in the early changeover one October in France. It's always a good thing for people who are traveling in spring or fall to check on. (Just one more detail for the list!)

We were on a tour in Turkey when, somehow, half the time changed-or something. Some people were on one time and some another. Pilots missed their planes, tourists missed all kinds of things. Very interesting. Fortunately, we didn't have to be anywhere that day.

I was in Granada over DST change 2 years ago. I had early morning entry tickets to the Alhambra the next morning, so I was definitely sweating that I get it correct particularly since I was still jet lagged.

Summertime starts 02:00 CET last Sunday in March.
Summertime ends 03:00 CEST last Sunday in October.

That's the standardised rule as defined for the whole of the EU. Other European countries mostly stick to the same dates to avoid confusion.
Outside Europe countries set their own rules and are different from each other (Russia, Turkey, North America etc.).
There is a proposal to abolish Summertime in the EU, this will "probably" happen in 2020.

Before EU standardisation different countries changed on different dates, France different from UK, and Germany didn't have summer time at all. You can imagine the confusion.

Spain really is on summer time in the winter and double summer time in the summer.

Spain really is on summer time in the winter and double summer time in the summer.

You could argue the same about France, due south of London, so it should be on GMT, but it is on CET (GMT+1/GMT+2).
Berlin is about right for CET, Netherlands, Belgium and Switzerland should be on GMT+½ hour. But as in the case of Spain, the advantages of being on the same time zone as your neighbours outweighs having a slightly false time.