In the friendlier AA Forum at FT .. lets direct the OP to some detailed information provided by AA.
http://www.aa.com/content/travelInfo...ralInfo.jhtml; states that
Baggage cannot be checked prior to the day of departure. If this is similar 'logic' to AA's One Day AC Pass .. a day is defined not in 24 hour terms but in the actual calendar day. Checking a bag at 11pm the night before will not work but at 12:01am the same day it should work (according to the aa.com web page that the OP may wish to carry for proof if the JFK peoples give them a hard time).