In California, if you are an hourly employee (or a salaried employee who is not exempt from overtime, whether because you earn too little [less than $23,600/year] or your job description does not meet the critera to be exempt), then yes, if actually *work* more than 8 hours in a day, you get overtime for all time past 8 hours. But only for time spent actually working: time spent being on call, if not working (i.e. if not called in to work) does not have to be paid and is not counted for overtime.