Does the time difference between Berlin and Los Angeles change during the year?

Yes. Because of daylight saving time the gap moves between +8h and +9h.

When is the best time to call Los Angeles from Berlin?

There is no overlap between standard working days, so one side has to call early or late.

Berlin is 9h ahead of Los Angeles. This gap is not fixed: daylight saving time moves it between +8h and +9h during the year.

Berlin

Germany

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Los Angeles

United States

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A 9-to-5 working day in Berlin does not overlap one in Los Angeles at all — somebody has to take the call outside office hours.

City	Time zone	UTC offset
Berlin · Germany	Europe/Berlin	UTC+2
Los Angeles · United States	America/Los_Angeles	UTC−7

What is the time difference between Berlin and Los Angeles?: Berlin is 9h ahead of Los Angeles. This gap is not fixed: daylight saving time moves it between +8h and +9h during the year.
Does the time difference between Berlin and Los Angeles change during the year?: Yes. Because of daylight saving time the gap moves between +8h and +9h.
When is the best time to call Los Angeles from Berlin?: There is no overlap between standard working days, so one side has to call early or late.