I'm in college now, and had an internship with a company in California last summer where HR did the exact same thing.

Apparently, it's California law that hourly employees can only work 8 hours per day, and anything over 8 hours in a 24 hours period is "overtime."

I'm now at an internship with a software company in New York, where the rules are what I consider "normal": Anything over 40 hours in a week is considered overtime, no matter when it was worked. However, the company has a strict no-overtime policy without (hard-to-get) prior approval.

For me, this meant I spent more of my time working in CA, because I was rewarded, while in NY, I work 9 hour days four days a week, then take off after lunch on Friday for a 2.5 day weekend.