The failure to appear at a court date in a criminal case results in the imposition of significant sanctions by the judge in most proceedings, according to "Criminal Law: Cases and Materials" by John Kaplan, Robert Weisberg and Guyora Binder.
Judges impose at least one of two penalties when a court date is missed: a bench warrant, directing law enforcement to arrest you will be issued and/or your bail bond, if you have one, will be revoked.
A judge typically issues a bench warrant and revokes your bond at the time of the scheduled hearing. These orders can take a day or two to work through the system, resulting in a short delay before the warrant is active.
If you legitimately cannot make a court date, notify the judge's administrative assistant immediately. Some valid reasons for not appearing in court as scheduled are a death in your immediate family or a serious health problem afflicting you.