What is the ruling on the fasting and prayers of those who live in lands where the night or day lasts for six months?

Allah Almighty informed us in the Holy Quran about a part of the story of Dhul-Qarnayn, and He withheld from us the specific land he reached, mentioning only the two directions he traveled to: the East and the West. There is no benefit in exhausting oneself trying to determine this land, because no action depends on it, and this is from the knowledge which one is not harmed by being ignorant of.