Calculating Months/Yr including partial months

Hello - I am trying to calculate the number of months in between two dates for a given year. The formula needs to take into account partial months as the number of days divided by the number of days in that month so 30 if November, 29 if February on a leap year, etc. The attached spread sheet shows for example what I need. I've been working on this for a while and can't get it right.

I started with lookups and countif and have a list of all days since January 2004 in a look-up range, but besides not giving me the exact answer there has to be a simpler way than listing all days in a lookup/reference table. Any help would be greatly appreciated!!