No, it’s not an outgoing weekly date. Mail gets sorted and transmitted to destination post offices every day. The only thing that happens once a week is delivery to / pickup from the community mailbox. And which day that happens on depends on which neighbourhood you live in.

Think of it like waste collection. It happens every day but each neighbourhood only gets collected once a week. I may get mine collected on Tuesdays but my friend who lives in a different area gets his collected on Wednesdays. Meanwhile, the normal operations of the landfill are running every weekday.

What this means is that the postal workers who just work in the post office sorting and filling trucks continue working every day as normal. However, the postal workers who drive around and fill up the community mailboxes will work a different route each day of the week. This means one postal worker can serve 5 times as many addresses as they currently do right now (where the same postal worker drives the same route every day). Additionally, that one worker will be carrying a full 7 days worth of mail to deliver to that community rather than only a single day worth of mail (or 3 days worth on a Monday).