In theory he could have been stalking the streets at 0300 on any given day. But on 2/26/2012 he was deceased by 1930.
Maybe he was out there that late to sell drugs or rob an all night gas station. Maybe, he was conspiring to get another gang tattoo or more gold teeth.
These are only things that Trayvon would have known and Zimmerman as a trained officer of the neighborhood watch would have observed.