The longest and shortest days of the year — the days when the sun is furthest from the Equator — are each called a solstice.
If you are on the part of the earth that is pointed towards the sun on the solstice, you are probably enjoying the longest day of summer. If you're pointed away, it is the shortest day of winter. Some people who do not believe in organized religion but like the idea of bringing lights inside and brightening a dark season celebrate the winter solstice, which falls a few days before Christmas.
