<p>Or do they open them as they come in? (assuming they have normal admissions, not rolling)</p>
<p>Office procedures vary from campus to campus, but I seriously doubt a college would wait until the deadline to start opening the mail. It would take almost their entire decision time to open the mail, log it into whatever system they use, file it, review files to see if they are complete, and assign them to a reader.</p>
<p>What fireflyscout said as for a general answer. Harvard specifically says that it begins reviewing applications already received on the first of December (or is that the first of November?), even though the application deadline isn’t until the first of January. At some colleges, it probably is a good idea to beat the deadline by weeks rather than by minutes.</p>