Find how many months between a certain date and the end of the year

 Hi In a report I want to find how many months between a date that is on a record (a maintenance end date) and December of either that year  or if the date is in December, then it will show the number of months until December - or the next December.

So for example for the following dates:

- 31/12/2012 - this would show me 12 (months) with the logic that the maintenance should be renewed up until 3112/2013

- 31/04/2012 - this would show me 8 (months) with the logic that the maintenance should be renewed until 31/12/2012  OR 20 (months) meaning renewal until 31/04/2013. 

Is this possible? 

Thank you