Hi, I am traveling from USA > Tokyo > Seoul > Beijing > USA. Will I be eligable for the 72 hr?

David, your route qualifies for the 72 hrs free transit policy.

I heard from someone that the 72 hours in Beijing start from the next day at midnight. However, this morning, a guy said that he called the Beijing Immigration and was told that the 72 hours start from the scheduled arrival time. Therefore, to play safe, I suggest you limit your stay in Beijing to the 72 hours calculated by the second way.