Date: December 21st, 2012
Korean singer PSY has beat out Justin Bieber’s “Baby” and Rebecca Black’s “Friday” as being the most viewed YouTube video, reaching 1 Billion views on December 21st, 2012. He also holds the title of “first video to reach 1 billion viewers”.
Source:
http://canhardleybelieveit.wordpress.com/2012/12/22/most-views-on-a-youtube-video-psy-gangnam-style/