We don't need a calendar to tell us it's Friday at this house. Everyone staggers into the house from work or practice or a meeting, and more than one coat doesn't quite make it onto the hook or hanger or chair back. Bags are carried just far enough to not be counted as left in the doorway.
It's common to find a shadowy lump in a chair or on a sofa in a room that is dark because flipping a light switch seems like too much effort. Often each person finds his or her way to a different room, too worn out for company. The energy level in the house would make a sloth appear hyper.
Even when someone has something planned, and even if it's a much anticipated event, the getting ready takes at least twice as long as usual. It's accompanied by deep sighs and sometimes a soft groan. Going and doing isn't the problem. The problem is momentum.
Dinner is late on Fridays. It takes a while to work up the desire to do something about the hunger pangs. Sometimes someone takes one for the team and agrees to go pick up carry out. Often it's the person who hasn't yet managed to change into sweats or pajamas.
Bedtime becomes a problem only because bed is so far away. There are stairs involved, and teeth brushing, and defying the gravity that keeps us pinned to our spots. There is no need for a calendar to tell us the day of the week. On Friday, we know.