I am confused about the duration and point in time.
a "He traveled two hours." b "He traveled Saturday." c "He traveled ON Saturday."
In a), "travel" is used transitively, in the sense of "he USED two hours." In b), "travel" is used INtransitively, because b) is a shortened version of c), in which "travel" is used INtransitively, and "Saturday" is a point in time, not d