Mine is definitely open on both Friday and Saturday so must be one of the select ones. I'm pretty sure it's a privately owned PO as opposed to the main one on the main street which keeps regular AP times. Mine has extended trading hours (7am - 5.55pm Mon-Fri and 7am - 11.55am Sat).

I'm certainly not expecting anything to go anywhere on Friday, but if I wasn't working myself, I know I can still post stuff and get a tracking number to say it's been posted inside the handling time.