72 hr free visa layover in Beijing

i wanted to do layover the 72 hr visa free stay in BJ. I am coming form USA arrive BJ sept 11,2013 1130
at night. By the time I get out of the airport after immigration and customs it will be sept 12 after midnight. My departure from BJ on sept 15 at 0100 am to Manila. I plan to get to the airport by 10 pm on the 14th. Is this still ok being at the airport before the 72 hr stay even though my flight is after midnight on 15th sept? Thanks.
Shirley Ferruzzi