Measured Travel Time
You can only do that if you have the timestamp stored together with the coordinates of the points. Other solutions are unrealistic. If you have both timestamps, then it is simple to calculate the difference in number of seconds.
Convert both times to "timeSinceReferenceDate" and subtrac:
something like deltaSeconds = abs(t2 - t1);
Estimated Traveltime automotive
If you have only coordinates, and want to know the estimated travel time by using a car, you have to use a routing service, which calculates the route and time duration for your you.