According to a post on the PlayStation Community Forums, PSN will be partially inaccessible for six hours on June 2nd whilst maintenance is done. The outage will occur from 9:50 a.m. to 3:30 p.m. PT/ 12:50 p.m. to 6:30 p.m. ET and during this period you will not be able to access PlayStation Home, your Account Management, or the PlayStation Store.
As long as you’ve signed into PSN from May 30th you will still be able to play online and use apps whilst the maintenance is taking place. This will also affect European players and for them the update will take place on the same day from 5:50 p.m. until 11:30 p.m. GMT.