Well ask and you shall receive. JSIN now has a website where he adds a little more information. I also asked directly if there's a specific time or if we just message him at midnight and he replied, "I'll just leave it open this time," which I take to mean yes, message him at midnight.
Edit: Now the website actually says message him at 12am PST.
So there we go.
Next preorder goes live 7/30.