How late can you write a deferral letter to a university?

I'm thinking of writing a deferral letter to a university, i have orientation in 2 weeks and should be leaving in 2 months so my question is how late can i request a deferral? I'm trying to decide currently weather to head off to said university or to stay close to my family/save money by going to another after a semester of community college but would like to keep my options open by deferring my acceptance