Legal Question in Employment Law in California

Not likely. Every employer must establish a start/end time for the work day, or the default is midnight. Most 9-5 businesses use midnight. "Round the clock" operations or those that operate in the evenings or nights, such as guard services, bars and restaurants, will commonly use 4, 6, or 8 am. Overtime is due per work-day, not per 24 hours. Most likely your work day started/ended at midnight, breaking the two shifts into two different days, and no overtime would be due.

To play off of what Mr. McCormick said - the situation would be different if you worked 8am - 4pm then were asked to come back and work 8pm - midnight on the same day. The last four hours would generally be overtime.