Summer Solstice, the longest day of the year in the northern hemisphere, is one of four solstice days marking the movements of the sun thru its seasonal cycle. It has a long tradition in pagan circles as Litha, and is considered the mid-point of summer, which begins with Beltane on May 1st and ends with Lughnasadh on August 1st. Some celebrate the triumph of Light over Dark, while others celebrate the coming harvest.
In the U.S., for those who aren’t pagans, it’s the beginning of summer, kids celebrating being out of school, and absolutely no holidays between July 4th and the first Monday in September, Labor Day.