I am getting blocked by this simple problem in a worksheet under construction with the objective to give a countdown to my relatives' birthday dates.

I want a formula to output for example "10" (as a positive number) when the birthday was on 5th May 2009 and the current date is (say) 25 April 2015. The difficulty comes when I want the formula to activate no more than 30 days in advance. I have been trying all combinations of the usual stacked if(), month() and day() functions but to no avail. Can anyone help? Tks