When is Edward Cullen's vampire birthday?

When did Edward Cullen become a vampire? I'm making a site for my daughter as a birthday gift,including a biography of Edward Cullen. I have read the Twilight book but unfortunately cannot remember the day he became a vampire. If you would be so kind to answer, I will e-mail you my site with your permission. If you would like to receive my site,put your answer and type yes. Thank you for your cooperation.