Which day is the longest day in a year?
Answer:
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 long. So technically the longest day is the day daylight savings ends, which is different for most countries. ;-)
Now, if the real question is what day has the longest amount of day light or "day time", then that would probably match the answer someone gave above. Yeah someone could argue the term "day" refers to the day light hours, but then ask yourself, how many hours in a day, it's 24 right, we don't say around about 12 depending on time of year.