Does the time difference between Berlin and London change during the year?

No. The gap stays at 1h all year.

When is the best time to call London from Berlin?

Between 10:00 and 17:00 in Berlin, which is 09:00 to 16:00 in London.

Berlin is 1h ahead of London. This gap is the same all year — neither city shifts its clocks relative to the other.

Berlin

Germany

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London

United Kingdom

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A 9-to-5 day in each city overlaps for 7h. That is 10:00–17:00 in Berlin, which is 09:00–16:00 in London.

City	Time zone	UTC offset
Berlin · Germany	Europe/Berlin	UTC+2
London · United Kingdom	Europe/London	UTC+1

What is the time difference between Berlin and London?: Berlin is 1h ahead of London. This gap is the same all year — neither city shifts its clocks relative to the other.
Does the time difference between Berlin and London change during the year?: No. The gap stays at 1h all year.
When is the best time to call London from Berlin?: Between 10:00 and 17:00 in Berlin, which is 09:00 to 16:00 in London.