Further, polar night in Tromsø ends around 21st of January, while the midnight sun starts around 21st of May - that's roughly 17 weeks going from the sun not rising, to the sun not setting - more than an hour of difference, week to week on average (0-24 hours, in 17 weeks).
[ed: of course, the change isn't linear: https://www.timeanddate.com/sun/norway/tromso ]