University of Michigan Early Action Decisions Release Date?

I understand that we are guaranteed our admissions decision by Dec. 24, but are these decisions rolling, or will they all be released on a single day sometime before Dec. 24? If so, what dates were they released in the previous years? Thanks

See http://talk.qa.collegeconfidential.com/university-michigan-ann-arbor/1963344-university-of-michigan-ann-arbor-class-of-2022-early-action.html#latest