I think perhaps there was a typo or misunderstanding. Based on the context, I think what the person was trying to say was, "The deadline was October 1st. Well, I guess the reasoning is that by October 1st the semester is [in] FULL gear." I added the word "in" to help give context. I believe they meant "full gear" instead of "for gear" because that would make more sense. The phrase "in full gear" means something along the lines of "already set in motion" or "off and running." Basically they are saying the semester would be well under way by October, as opposed to just starting or just ending.

gear = 具 It is the stuff you need in order to do something. College gear = books, pencils, etc. I'm not really sure why one would need a whole semester though.

I found the dialogue which you quote from, and sorry to say, it wasn't written by a native speaker (pretty obvious). The only sensible meanings I can ascertain are: gear = stuff; gear = fun (gear, from "great"... fairly obscure); gear = a run-up.