It seems that a rather loosely organized hippie gathering took place in a Canyon (presumably Laguna Canyon) east of Laguna Beach, CA starting on Christmas in 1970 and ending on Monday, 12/28. It was broken up by city police, who in good Orange Curtain fashion sang "Here Comes Santa Clause" as they rousted sleeping hippies and dropped them off at the city limits.
According to the report (1), the Grateful Dead came to play, but were "not permitted through the barricades, which were set up to halt the heavy flow of traffic into Laguna Beach." The report isn't clear about the day on which this occurred. The GD were playing Legion Stadium in El Monte, about 60 miles away, from 12/26-28, so whatever day it was --I'll assume Sunday, 12/27-- they presumably came out during the day time. I bet it would have been a good ol' time, but, alas, it was not to be.
Gordon Grant and William Endicott, "Stragglers Sound Final Notes at Laguna Beach Rock Festival," Los Angeles Times, December 29, 1970, pp. A1, A3.