Q. Which day of the year is the longest in the Northern Hemisphere?
Ans. It is 21st June of every year it is the time of summer Solstice.

Q. Which countries can experience 6 months day and 6 months night?
Ans. The Sun rises at the North Ple on the 21st March and this pole remains in light till the 23rd of September. We can see the sun even at night for some months at places near north pole like Norway, Greenland and Northern Russia.