This Web page tells you how many days old you are and on which day you were born:
http://www.korn19.ch/coding/days.php Just enter your birth year, month and day.
The website was created by a student who lives in Switzerland and is studying programming at the University of Zürich, according to the website (in 2013). The student says in the "about" section of the website, that he "loves programming in PHP and know a bit of Java and C++ thanks to university courses."
* The number of leap years you have lived through actually shows how many February 29's you've been in. For instance, someone born in August 2012 will have 0 leap years because he was born after February 29th.