This is not required on the calendars AND it would add cost to the printing/binding process. Personally I don't need or want it but a pocket for one with a hanger tab would solve the issue and not add a lot of cost. User provides his/her own dowel if required.
Mark has done a good job and we all need to think production cost also. Adding more bells and whistles to a good product only drives the cost up and we would all have to pay more. Larger type (numbers), less/more pictures, additional info on the blocks, etc. would add little to no production cost.
I will take another look and see if I can come up with something BUT I think its great as it is.