Global Trade Station

After battling your rival, if you just save without moving out of the current screen, your rival will be available again for battle when you turn on your ds on other days as well.
At least that happened to me, I battled him in the weekend, and even though its Thursday he was ready for a new battle when I turned on my ds today. I'm not sure if this work many days in session though, does anyone know anything about this?

Um....I think that is supposed to happen. It happened to me.

ok, but he's usually only avaible for battles on saturday and sunday:-/

it's cause you saved it while he was on the screen
so you saved it on his current state.
in the game programing, that state tells him to battle you any other day, but when you see him by walking near him, he is reloaded and is set to not battle you because of the date.

es he appears in the in the battle place every weekend

No, the game has an inbuilt clock. ITime passes whether you're onit or not.