University of Michigan's student business site (registering classes, bills, transcripts, etc.) is closed from 4am - 6am every day and 11pm Saturday - 7:30am Sun

University of Michigan's student business site (registering classes, bills, transcripts, etc.) is closed from 4am - 6am every day and 11pm Saturday - 7:30am Sunday. I hit this period several times without knowing what was wrong. The warning isn't very obvious.