January 20th
The date January 20th is significant because this is when a new president is inaugurated. The predecessor is remaining in the residence until January 19th, so the newly-elected president can only move in on January 20th and has a mere 12 hours to do so.
The Procedure for Moving in
Many security issues come with moving into the White House. For these security risks, the new First Family is only allowed 12 hours to move into their new residence. The fastest record goes to the Obamas who took five hours to move into the White House.