Hi ify,
They have started to mail them out. They have three interview weekends, the first one coming up on Feb. 20th. I am pretty sure that all the invites for that weekend have gone out. They keep sending invites into mid-march, as the last weekend, if i remember correctly is in early April. The weekends are in no way ranked, meaning that if you interview on the first weekend, it does not mean that u were ranked higher than those who are interviewing on the last weekend.
Good luck!
thesaug