Disney has slightly bumped up the release date for Mary Poppins Returns from Christmas Day to 12/19. This may not seem like that big of a deal, but with Christmas on a Tuesday this year, moving the film's release up to the prior Wednesday may signal confidence in its box office potential from the studio. By the time Christmas Day comes to a close, we will have a full seven days of receipts to take the temperature of the film's reception.
This move will also wreak havoc for other studios, who are now likely going to have to reconsider their slates for the entire month of December. I doubt Disney is too worried about it.