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

Yes. Because of daylight saving time the gap moves between −6h and −5h.

When is the best time to call Jakarta from Berlin?

Between 09:00 and 12:00 in Berlin, which is 14:00 to 17:00 in Jakarta.

Berlin is 5h behind Jakarta. This gap is not fixed: daylight saving time moves it between −6h and −5h during the year.

Berlin

Germany

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Jakarta

Indonesia

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A 9-to-5 day in each city overlaps for 3h. That is 09:00–12:00 in Berlin, which is 14:00–17:00 in Jakarta.

City	Time zone	UTC offset
Berlin · Germany	Europe/Berlin	UTC+2
Jakarta · Indonesia	Asia/Jakarta	UTC+7

What is the time difference between Berlin and Jakarta?: Berlin is 5h behind Jakarta. This gap is not fixed: daylight saving time moves it between −6h and −5h during the year.
Does the time difference between Berlin and Jakarta change during the year?: Yes. Because of daylight saving time the gap moves between −6h and −5h.
When is the best time to call Jakarta from Berlin?: Between 09:00 and 12:00 in Berlin, which is 14:00 to 17:00 in Jakarta.