How to know the time it takes to arrive at rallying location?

When you join a rally you will see the time it takes for your legion to march to the leaders city. And also the time remaining before the rally departs. There is no way to see how long the actual rally march is but you can tap on the targets location in the rally listing to find it on the map and you may be able to tell how far it is from the rally leaders city to see if it is a long march or a short one.