Dear Jim: Why Sunday the 13th?
Because the Japanese Pearl Harbor attack was announced around noonish in the US on a Sunday. It collected and brought the people together, where they were, collected as family. It is the precedent best time for such an announcement. Because that precedent kept panic down, such as "what about the kids in school", What about last minute shopping - I don't get off work for another 6 hours. On a Sunday mid-day, family can openly brainstorm, plan, communicate and react before the work-week begins. Because it does not disrupt the workplace and create accidents. Because the 13th is five days after the voting date of the 8th, which is way after vote counts should be in and accounted for. And because that is time enough for the Biden administration to show their cards. Finally, it also dovetails with Clif High's projection of the 13th.