In the Northern Hemisphere, the longest day of the year in terms of daylight, is the Summer Solstice, which will occur on June 20, 2021. The Sun will reach its northernmost position, as seen from the Earth. At that moment, its zenith does not move north or south as during most other days of the year, but it stands still at the Tropic of Cancer. It then reverses its direction and starts moving south again.