Does the time difference between Dubai and London change during the year?

Yes. Because of daylight saving time the gap moves between +3h and +4h.

When is the best time to call London from Dubai?

Between 12:00 and 17:00 in Dubai, which is 09:00 to 14:00 in London.

Dubai is 3h ahead of London. This gap is not fixed: daylight saving time moves it between +3h and +4h during the year.

Dubai

United Arab Emirates

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London

United Kingdom

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

City	Time zone	UTC offset
Dubai · United Arab Emirates	Asia/Dubai	UTC+4
London · United Kingdom	Europe/London	UTC+1

What is the time difference between Dubai and London?: Dubai is 3h ahead of London. This gap is not fixed: daylight saving time moves it between +3h and +4h during the year.
Does the time difference between Dubai and London change during the year?: Yes. Because of daylight saving time the gap moves between +3h and +4h.
When is the best time to call London from Dubai?: Between 12:00 and 17:00 in Dubai, which is 09:00 to 14:00 in London.