The fall or autumnal equinox arrives today.
According to the Washington Post, the equinox occurs when the sun crosses the equator, making day and night of roughly equal length all around the world.
In the Bay Area, this crossover happens at 7:49 am.
If you're looking for a celebration to go with the season, the AT&T Autumn Moon Festival runs from 11 am to 6 pm in San Francisco's Chinatown.
Just looking to get outdoors but reluctant to cross the Bay? Oakland puts on a lovely art stroll on Saturday afternoons.
Or enjoy a day of history and fun at Casa Peralta in San Leandro.
If your activities take you away from home, consider riding BART. The transit system is celebrating its 40th anniversary by handing out 1,000 free passes. Could this be your lucky day?