The Apple Worldwide Developers Conference keynote clashes with Microsoft's E3 presentation.
Apple will unveil iOS 5, Lion and iCloud at a keynote this Monday, 6th June at 10am.
Microsoft begins its E3 press conference 30 minutes earlier.
Apple core Steve Jobs will deliver the keynote flanked by a team of execs - pips.
The keynote kicks off Apple's Worldwide Developers Conference, where more than 100 sessions explore all areas of Apple's enviable technology and software.