the dance is happening as soon as possible, if you start making posts in the g building about people moving chairs and such then the dance will be happening.
Damon sees the cafeteria staff, which have appeared from seemingly nowhere, moving tables and stacking chairs. He drops his tray off and heads back for the dorm.
EDIT: Apparently I failed to post anything regarding what happened after I left the cafeteria "yesterday", so we'll just assume Damon made it back to his room okay. Unless of course something awful happened while no one was looking, in which case Nunu will set me straight.