That is correct. The midnight mass fulfills the mass of the day. It is the case for Christmas day and it is the same for Easter. That is, the Easter Vigil fulfills the obligation for the Easter Day mass.
As to this year’s Christmas being on Sunday, it does not make a difference. The midnight mass is called midnight mass, precisely is to tell us it is for the next day,, even though nowadays the so-called midnight mass takes place way earlier than midnight.


