December 22, is Winter Solstice, the shortest day of the year in the Northern Hemisphere. In the Southern Hemisphere, conversely December 22 is Summer Solstice − in places like Australia, New Zealand, or South Africa, therefore, December 22 is the year's longest day. This situation will be reversed after six months from. On June 21 , every year, the Northern Hemisphere will see the Summer Solstice when the day will be the year's longest. And the Southern Hemisphere will see the year's shortest day - or longest night.