Graduate students cannot use Student Center to update their graduation date. The student should have found a message in Student Center informing them that they need to go to their department office and file a warrant, which is the way that graduate students apply for graduation.
This is the message that the student should see:
Graduate career (G918) Graduate students MUST contact their graduate program coordinator to declare their intent to graduate. Check the following web sites for specific deadlines:
Graduate students who wish to attend a commencement ceremony that does not coincide with their anticipated date of graduation should contact the Secretary of the Faculty's Office at (608) 262-3956 so that your name will appear in the commencement program.
If the student has some questions about their eligibility to graduate or whether or not the information has been recorded, they will need to contact their graduate school academic affairs office to find out.