Beijing 73 hours?

We fly into BEIJING at 1:05am on May 1 and fly out May 4 at 2:30am. That'll be 73 hours and 25 minutes. Is Beijing Airport strict? I have read that all other airports the clock actually starts the next 00:00, which would mean we could technically stay an extra 23 hours, but because we're flying into Beijing we can only fly in 1:05am and then fly out 3 days later at 1:05am again (instead of our fly out 1.5 hours later at 2:30am)?