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

No. Both cities keep the same local time all year.

When is the best time to call Paris from Berlin?

Between 09:00 and 17:00 in Berlin, which is 09:00 to 17:00 in Paris.

Berlin and Paris are on the same local time. This gap is the same all year — neither city shifts its clocks relative to the other.

Berlin

Germany

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Paris

France

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A 9-to-5 day in each city overlaps for 8h. That is 09:00–17:00 in Berlin, which is 09:00–17:00 in Paris.

City	Time zone	UTC offset
Berlin · Germany	Europe/Berlin	UTC+2
Paris · France	Europe/Paris	UTC+2

What is the time difference between Berlin and Paris?: Berlin and Paris are on the same local time. This gap is the same all year — neither city shifts its clocks relative to the other.
Does the time difference between Berlin and Paris change during the year?: No. Both cities keep the same local time all year.
When is the best time to call Paris from Berlin?: Between 09:00 and 17:00 in Berlin, which is 09:00 to 17:00 in Paris.