Legal Question in Employment Law in California

No employer is obligated to pay you for time you don't work, except that if you show up for a scheduled shift they must pay you at least 1/2 your pay for your "regular" shift, but not less than two hours, nor more than four unless you actually work more than four. It doesn't matter why they don't work you the full shift, whether it is a fire, or they're just slow, or any reason at all. So as long as they are paying you for at least two hours, or half your regular hours up to four hours, they are paying you all they owe. If you want a full day's pay for the rest of the day, they are not required to but are allowing you to use PTO.