Here in Sweden, these ISO week numbers were super popular with the older generation who were constantly pushing them and referring to them, much to the confusion of us in the younger generation. (I'm old now, but this was in the 90s and 00s.) A shop clerk or gov't employee or parent would suggest a date like "how about week 43?" and I'd have to go "uh… and what date does that week start on?" and they then would go look it up or I'd have to do it.

I've noticed that this isn't as much of a problem anymore, maybe because smartphones and internet aren't set up around this kinda weekly date. My parents' generation, my teachers, people calling from the hospital, or postal deliveries etc would all say "how about Thursday in week 43?" instead of what's more common now, which is "how about October 26th? That's a Thursday."

But maybe I should bring week numbers back into my life? GTD works well on a week-by-week basis (and I'm experimenting with switching back to paper; I first switched to digital in February 2010), and so does my roleplaying group.

(One thing that doesn't work well on a week-by-week basis is my hair; untangling & cutting the split ends every sixth day is OK but seven days is pushing it. Twice a week would be great but seven is a prime 🤦🏻‍♀️.)

https://en.wikipedia.org/wiki/ISO_week_date