If you go to this wikipedia site you can find out what the number 1 song was for various weeks in the past.
I decided to focus on my graduations up to my Ph.D., as that was the biggest time of my life. The songs seem to have gone down in terms of quality in my mind from birth to the time of the Ph.D., but I'll leave that up to others to decide.
What songs were number 1 at key moments in your life? What would those key moments be?
For me they're the following:
Birth: April, 1969: Aquarius/Let the Sunshine In H.S. Graduation: June, 1987: With or Without You B.S. Graduation: December, 1991: Black or White M.S. Graduation: May, 1996: Always be my baby Ph.D. Graduation: May, 1999: Livin La Vida Loca