Where you are working makes no difference. Who you are working for and in what capacity makes all the difference. For most public employers and all private employers the state wage orders determine your right to overtime and when. Then it is a matter of what job you do and whether you are "exempt" or "non-exempt." If you are in most job classifications and are non-exempt you would be entitled to overtime for any time over 8 hours in a day and over 40 hours in a week, but you can't double dip. So if you work 8 hours on Monday, and 10 hours on Tuesday, you get two hours of overtime for Tuesday, but then if you work 6 hours on Wednesday, and 8 hours Thursday and Friday, the first two hours on Saturday would be regular time. You don't get to double dip overtime for 4 hours when you have only worked 42. In other words, you have to accumulate 40 hours at regular time before you start getting overtime on the basis of being over 40 hours a week.

The only issue is, if you are an hourly CA employee, not 'salary exempt' status such a mgmt or professional or a few other similar classifications [which you would know about if you were], you are to be paid OT for anything over 8 per day and 40 per week. No mystery or surprise there. If you aren't properly paid, you are entitled to file a claim with the CA Labor Commissioner's office for unpaid compensation, penalties, interest, and attorney fees if you win a contested claim. You'll have to be able to prove your hours worked if there are no time keeping systems.