Upon approval of the dissertation, make sure your final draft follows formatting guidelines. The Graduate College dissertation inspectors are thorough. Follow dissertation format guidelines to the letter: Thesis Manual.
The deadline to submit a dissertation to the Graduate College is always well in advance, by mid-March for May graduation and by early July for August graduation. And you must apply for graduation. See the Graduate College Graduation page for details.
If you intend to publish your dissertation, consider William Germano’s well-received book, From Dissertation to Book, for sensible advice. It may not be a bad idea to read the book before you begin to write your dissertation.