Bring it to the post office but DO NOT make an issue out of the date. Leave it on an open counter or drop it in the internal chute.
Some sellers will tell you that the post office is fusy abut the date vs the date mailed. But I suspect that is only because they drew attentuion to it. Slid it in and walk away.
"Laissez-faire capitalism (AKA The Great Material Continuum) is the only social system based on the recognition of individual rights and, therefore, the only system that bans force from social relationships." ~ Ayn Rand
