Perhaps she is just getting all her sales ready the day before to shoot out the door in the morning and go to the PO to post on her way to work, or some other appt.

Just getting ahead of the game I would think, or as some others have suggested she might have gone to a PO box and dropped in.

The best way to track and get confirmation of actual posting is to watch the item on AP's website.

Personally I wouldn't have a problem with showing as a Sunday, I would think that they are super organised. 

Wish I was!