The office is open in the weeks leading up to semester one and I'm reasonably sure I saw it open when I was handing stuff into the SOPHI office today, so it should be open. Best to do what velox suggested and ring up beforehand.
Well, the science student center was open a couple of weeks before o-week this year, and I imagine that the arts faculty office would serve more student than the science one. I expect they'd be open all year round. Right?