Just for clarification sake, the time element does not take into consideration the other 2 prerequisites of a catch.
a) secures control of the ball in his hands or arms prior to the ball touching the ground; and
b) touches the ground inbounds with both feet or with any part of his body other than his hands; and
c) maintains control of the ball long enough, after (a) and (b) have been fulfilled, to enable him to perform any act common to the game (i.e., maintaining control long enough to pitch it, pass it, advance with it, or avoid or ward off an opponent, etc.)
Control with 2 feet doesn't satisfy the time requirement because the element of time must occur after control with and a 2nd foot.
From the perspective of satisfying the element of time, whatever magical stopwatch the NFL would use would begin after his 2nd foot.