Tonight start of summertime (daylight saving time) 2017

Today, Daylight Saving Time ('Zomertijd') 2017 will start in the Netherlands, and throughout the rest of Europe.

At 2am in the night from Saturday to Sunday, the clocks are moved forward one hour, to 3am. This will happen in all member states of the European Union (except in Britain, where clocks will be moved forward at 1am).

The change will mean darker mornings but longer day light in the evenings.
During the summer months in the Netherlands it remains light until as late as 10.30pm.

The time will go back to winter time in the last weekend in October.

Please find everything on the subject in Wikipedia.