You don't get overtime for working >8hrs a day, you get OT for >40hrs a week. So you'll get paid the equivalent of 14.5 hours for that day, but not extra because it was so long that day. But your tips are likely to be UH-may-zing also.

In most cases working Christmas Day should give you double time to my knowledge 🤔 at time and a half you'd be paid for 14.5 hours roughly, I'd assume maybe 2-3 hours approximately for overtime pay on top of that working anything over 8.