بسم الله الرحمن الرحيم
(Fatwa: 797/683/D=11/1437)
In the reply of such a question it is written in Fatwa Mahmoodia that the place where the length of the day is more than eighteen hours the healthy people of the place usually are habitual to bear such a long day. Hence in that place the same long day shall be considered, there is no need to calculate it otherwise. Hence in the question mentioned above the fasting of Sweden shall be according to their day of twenty hours. (Fatwa Mahmoodia: 10/32, pub. Darul Maarif)
Allah knows Best!
Darul Ifta,
Darul Uloom Deoband