Complex sentence: The PlayStation Network had an outage which began on April 20,2011 and affected 77 million registered accounts, is the longest amount of time the PSN has been offline since its inception in 2006.
Split into simpler sentences: The PlayStation Network had an outage which began on April 20,2011 and affected 77 million registered accounts. Lasting 23 days, this outage was the longest amount of time the PSN had been offline since its inception in 2006.