funny thing about time travel, it doesn't matter when things happen ^^
It does when there isn't a moment where the time machine could possibly be stolen by Haruhi. It was either in a time before Haruhi was born, was in use/being watched, or was being stolen by Biff. Time still matters when you're dealing with someone who doesn't have a time machine yet.
Look, Kyon! Get in my machine right now and we'll warp to Sunshine Creation on the 18th!Hey, Haruhi... A certain old guy somewhere is going to be bawling his eyes out if you use that in such a pitiful way.