OK, stools. Bowel movements....dropping kids off at the pool, whatever term you use, I have a movement every weekday at approx. 5pm.
Come the weekend, this movement happens first thing in the morning, then Monday arrives and its back to the 5pm slot - does anyone know why ? At least Im regular lol.
I concur that this will probably be down to the degree of mental relaxation you require in order for the said goods to be delivered.
You are more relaxed during your Friday night / saturday night sleep and so the delivery is brought forward.