I think it is because of the CHOC walk. They delay opening on that day and switch around when MM falls if it happens on a MM day. I'd have to look up that date to be sure, but that is probably why.
ETA, I just looked and yes the CHOC Walk falls on the 16th so that is why the MM is pushed to the Monday.
YAY!! I am glad that it is right. Especially since we will be staying at the DL hotel for Sun and Mon night. Now we will two bonus magic mornings. Thanks for the info.