Jeff Moden (7/16/2015)
I still want to know what someone considers to be a month. DATEDIFF(mm,'20150630','20150701') will say that a month has passed when only 1 day will have passed. What is the definition of a "month" for this case? 30 Days? 30.2 days? 4 Weeks? 5-4-4? What?
I guess the definition of a month for this case is very simple as the OP is not dealing with days, just a year-month combination.