Update: Sony has responded, stating that the report from a moderator on the European PlayStation Forums is incorrect. "SCEA can confirm that PSN maintenance is not happening this week. We'll keep you updated on all official PSN maintenance announcements on PlayStation.Blog."
The Sony representative notes that all official PSN maintenance announcements will always go through the PlayStation Blog and never through its forums or other avenues.
The original report is below...

An interesting tidbit can be found on the European PlayStation Forums concerning PlayStation Network maintenance that’s scheduled to occur on Wednesday, June 20th. Another post about it can be found here.
The information was posted by user SuperFastZombie, marked as a “Community Team Moderator.” The time of the maintenance is marked as 16:00-20:30 BST (British Summer Time). For American users, that equates to 11am-3:30pm ET / 8am-11:30am PT.
The forum post notes that “for the duration of the maintenance some users will be unable to log into the PlayStation Network, Account Management and the PS Store. PS Home will also be unavailable. There may be some additional downtime after the maintenance period for testing purposes.”
Because of the rather strange way this maintenance is being announced, we’ve reached out to Sony for confirmation (including on if this will only affect European PlayStation gamers) and will update when we hear back.