Round trip layovers in Beijing

I have a round trip ticket from NJ to Tokyo with a 13 hour layover in PEK which would result in an overnight stay each way.
Do I need a visa to stay overnight in BJ? Does the 72hr free transit apply, and if so what time does the administration office close. I arrive at 2:30 pm the first layover and coming back for this layover I arrive at 5:30 pm. Will the administration office still be open.