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

Yes. Because of daylight saving time the gap moves between 0 and +1h.

When is the best time to call Lagos from Berlin?

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

Berlin is 1h ahead of Lagos. This gap is not fixed: daylight saving time moves it between 0 and +1h during the year.

Berlin

Germany

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Lagos

Nigeria

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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 Lagos.

City	Time zone	UTC offset
Berlin · Germany	Europe/Berlin	UTC+2
Lagos · Nigeria	Africa/Lagos	UTC+1

What is the time difference between Berlin and Lagos?: Berlin is 1h ahead of Lagos. This gap is not fixed: daylight saving time moves it between 0 and +1h during the year.
Does the time difference between Berlin and Lagos change during the year?: Yes. Because of daylight saving time the gap moves between 0 and +1h.
When is the best time to call Lagos from Berlin?: Between 10:00 and 17:00 in Berlin, which is 09:00 to 16:00 in Lagos.