Does the time difference between Stockholm and Tokyo change during the year?

Yes. Because of daylight saving time the gap moves between −8h and −7h.

When is the best time to call Tokyo from Stockholm?

Between 09:00 and 10:00 in Stockholm, which is 16:00 to 17:00 in Tokyo.

Stockholm is 7h behind Tokyo. This gap is not fixed: daylight saving time moves it between −8h and −7h during the year.

Stockholm

Sweden

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Tokyo

Japan

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A 9-to-5 day in each city overlaps for 1h. That is 09:00–10:00 in Stockholm, which is 16:00–17:00 in Tokyo.

City	Time zone	UTC offset
Stockholm · Sweden	Europe/Stockholm	UTC+2
Tokyo · Japan	Asia/Tokyo	UTC+9

What is the time difference between Stockholm and Tokyo?: Stockholm is 7h behind Tokyo. This gap is not fixed: daylight saving time moves it between −8h and −7h during the year.
Does the time difference between Stockholm and Tokyo change during the year?: Yes. Because of daylight saving time the gap moves between −8h and −7h.
When is the best time to call Tokyo from Stockholm?: Between 09:00 and 10:00 in Stockholm, which is 16:00 to 17:00 in Tokyo.