“Norway is considered one of the best places to observe the amazing phenomenon of midnight sun.North Cape in Norway, which is the northernmost point of Europe, is known to have midnight sunfor about 76 days from May 14 to July 30. Other places of Norway, where you can see thisextraordinary natural phenomenon are Longyearbyen (Spitsbergen), Hammerfest, Tromso,Hausberg, and Narvik.”

“In Hammerfest, the ideal time to view the midnight sun is from May 16 to July 27, while April 20 to August 20 is the best time to go to Longyearbyen for this purpose. In Tromso and Narvik, themidnight sun is visible from May 20 to July 22, and May 25 to July 18, respectively. Apart fromNorway, Greenland, Northern Iceland, Finland, Northern Sweden, Canada, and Fairbanks, Alaska(USA) are some other good places to see the phenomenon.”

https://www.scribd.com/document/270568073/What-is-the-Midnight-Sun-Phenomenon

I think it depends on your location.
I believe at the North Pole it would be approximately 6 months from April through September. The further South you go, the later in the year it would begin and the shorter the time frame I assume.

Yes—this question is about at the Arctic Circle, such as Narvik, Norway and Kiruna, Sweden