The current rule
Germany moves to Mitteleuropäische Sommerzeit at 01:00 UTC on the last Sunday in March, which is 2:00 a.m. local, and back at 01:00 UTC on the last Sunday in October, which is 3:00 a.m. local. Winter is UTC+01:00 and summer UTC+02:00. Because the EU rule is written in UTC, every member state changes simultaneously rather than at a common local hour.
Germany invented it
Germany and Austria-Hungary were the first countries in the world to adopt daylight saving nationally, on 30 April 1916, as a wartime measure to conserve coal. Britain followed within weeks and the United States in 1918. The idea had been proposed decades earlier — by the New Zealand entomologist George Hudson in 1895, who wanted more evening daylight for collecting insects — but it took a fuel crisis to make it policy.
Where the EU proposal stands
The European Parliament voted in March 2019 to end seasonal clock changes, with each member state choosing permanent summer or winter time. It has never been implemented. Member states could not agree, partly because a patchwork of permanent choices would fragment the single market's time zones, and the file has sat unresolved ever since. Germany continues to change its clocks.