The longest day of the year for people in the Northern Hemisphere is on June 21. This marks the summer solstice when the sun is exactly overhead on the Tropic of Cancer at 23.5 degrees latitude.
On the summer solstice, there is maximum daylight and the night is very short. This is the peak of summer in the Northern Hemisphere. In the Arctic Circle, there are 24 hours of daylight, as the sun does not set.
This day marks the winter solstice for regions in the Southern Hemisphere. Australia and New Zealand experience winter with very short days and long nights. In the Antarctic Circle, there are 24 hours of darkness.