I read somewhere that they're open from 9am - 10pm EST. I'm not certain though. I just got off the phone with them 10 minutes ago (called at 7:30pm and was on hold for 20 minutes).
I'm leaving on May 16 and still haven't received my tags. The CM said we could give our claim tickets to the CMs at the airport or we could claim our bags and take them to the welcome centre.