SQL & PL/SQL :: Calculate Date When Contract Can Be Terminated

I've got the following table:

ID.................Date...........................number...period.....termination
434473......2012-04-18 00:00:00.000...............6.......month(s)...end of month
443080......2012-02-26 00:00:00.000...............36......month(s).....end of quarter

Now it's getting complicated. Date is the start date of a contract.

I need to calculate a date when the contract can be terminated and must compare it with the current date. Lets take the first row. In column "termination" is the termination date. A contract can be terminated at "end of month" (I need to check the last day of a month. In order to get the real termination date we need to subtract the column "number".

example 30.01.2012 - 7 month = 30.06. 2011

The thing I can do it, but my logic works only if the date is in the same year. I've been thinking a lot...sql is not important first....Have you got a theoretical solution?