June 21st is the summer solstice in the northern hemisphere and also the longest day of the year, at 14 hours, 46 minutes and 53 seconds (in San Francisco). It happens when the sun reaches its northernmost point in the sky.
Although the summer solstice is celebrated around the world, some say it started as a pagan ritual with the Midsummer's Eve celebration - bonfires, feasting and rituals. Stonehenge has a big celebration every year. There is a summer solstice celebration at San Francisco's Ocean Beach near Taraval starting at 8PM.
John M Scott, Broker / Owner, Scott Keys Properties, Certified Distressed Property Expert (CDPE), Council of Real Estate Brokerage Managers (CRB), serving San Francisco and the surrounding San Francisco Bay Area