What was the number one song on your birthday? That is the theme song of your life... well... according to this site anyway. AND, if you were born before 1952, your theme song is actually the date of your 18th birthday... which may actually work better anyway.
My actual birthday theme song:
Aquarius / Let The Sunshine In - 5th Dimension
My 18th birthday theme song:
(I Just) Died In Your Arms - Cutting Crew
There you have it... just one more insidious time waster that I have the privilege to pass along to you.