Daughter, 24 and not married. You know your biological clock is ticking.
Not usually used to describe night and morning people. She's a bit of a night owl. She's not a morning person.
I woke at 3AM, I think my biological clock is still on Beijing time. <-- not so common.
I woke at 3AM, I think I'm still on Beijing time. <-- more common.
You could also look for circadian clock/cycle, but not really a daily use phrase.