Here is the link to the library guide that has all the deadlines listed: http://libguides.caltech.edu/theses.
The rule of thumb from the Grad Office is that dissertations should be deposited within 2 months of defense. If the student is defending within 2 months of graduation, they’ll obviously have less time. For the latter, two weeks before graduation is the official deadline.
There are usually a few students who defend after the last date. They should be in contact with the Grad Office to ensure that the office has them on their radar for graduation. Iti is easier to take the students off the graduation list than to add them.
A student who has not completed all their graduation requirements by the Wednesday before graduation, when the final faculty meeting occurs, will not be able to graduate that year.