The problem is you can not generalize this to the whole department. Different branches give acceptances on different days, there is also the waitlist process.
Moreover they don't really wait weeks to send a rejection email, it is usually one day after they gave the final acceptances, afterall waiting for weeks to send a confirmed rejection letter does not make sense.
Again I have only seen some admits on 20th of February and silence since then. 3/1 may be a rejection day but they might give some acceptances till Friday.
BTW it seems they started giving out rejections...