That completely depends on your latitude ... how far you are from either of the earth's poles. At the pole itself, the longest day of the year lasts six months.
All days have the same length, everywhere on earth, namely, 24 hours. If you're asking about the longest period of time that the sun stays up, that's going to depend on where you are on earth. Here's...
June 21 Updated: Almost every day is 24 hrs, with exception of day light savings when clock is put forward an hour so that day is 23hrs, and when it ends, clock is put back an hour that day is 26 hrs...
The Summer Solstice is the longest day of the year and occurs in 2010 on June 21 in the Northern Hemisphere; and on December 21 in the Southern Hemisphere. There are 2 solstices: summer in the...