In my experience, right now is the time to watch a rub line. If anything, it will show you the bucks travel route. Later in the season it won't be nearly as effective. A buck will be more concerned with how the doe are traveling.
If you have an idea of which direction the bedding and feeding areas are, you might be able to tell if its morning or evening that the deer is making the rubs. If all the rubs are on the same side of each tree, then the deer is making them headed in the same direction each time. If it appears headed toward a bedding area, then he may be making them in the morning. If it appears headed toward the feeding area, then he may be making them in the evening.
Of course, all of this follows the rule that deer don't have rules and anything can happen, or it might give you some insight, who knows. He could be making them at night too. Hope this helps, or even makes sense.