It's only 4 conferences, two for an hour, two for an hour and a half. Heck Nintendo's isn't even until tomorrow, that sure is a big name in my book :P . The fact remains E3 begins tomorrow. Today is just pre-gamming for the event, it's not the event.
To make it more understandable: It's the same in-game. Watching the Ifrit/Moogle/Garuda cutscenes at the time you zone in isn't the fight; the fight hasn't even begun. It's not until you begin attacking does the fight begin and thus, not until the expo doors are open to the public does the event begin.