The date is considered lucky according to Chinese numerology and tradition because it is the eighth day of the eighth month of 2008, or 08/08/08, the clerk's office reported.
All 19 spots were booked within a week of when Aug. 8 became available, which was 30 days in advance of the date, Deputy Clerk-Assessor Theresa Rabe said.
Only two couples had requested ceremonies for the date since it filled up, according to Rabe.
The county chapel, which holds up to 25 people, also has an Internet connection so friends and family members who cannot make the ceremony can watch it live via the Internet.
Anyone wishing to get married in the county chapel, on a date other than Aug. 8, should call (650) 363-4500 to inquire about reservations, according to the clerk's office.