Overview: California's overtime is based on an 8-hour day and 40-hour workweek, unlike most other states who work off of a 40-hour workweek. It is detailed here: http://www.dir.ca.gov/dlse/faq_overtime.htm
How does an employee earn overtime or double time in California?
Employees can earn overtime or double time under the following circumstances:
Overtime for working beyond 8 hours in a day
Double time for working beyond 12 hours in a day
Overtime for working beyond 40 hours in a week
Overtime for working 8 hours on the 7th consecutive day.
Double time for working beyond 8 hours on the 7th consecutive day.