Thesis Defenses are open to the public and must be scheduled in advance to ensure they meet all administrative requirements for graduation.  The first step is working with your thesis committee to find a time everyone is available.  Do this at least five weeks before your defense.  Once you have agreed on a time and date, email the time, date, thesis abstract, and name of committee members, to, no sooner than two weeks prior to your defense .  They will find a room for the defense, post all the necessary public announcements, and provide all the necessary paperwork.