As a Swede I'd say week numbers are pretty ubiquitous in Sweden, with perhaps the first exposure to using week numbers being primary school. I remember counting down to week 9 (spring break) and, I guess, all the other breaks too.

Aside from this though, I could never quite get the hang of week numbers and always just found them more confusing than using dates. When my friends say they're going on their summer holidays in weeks 30-32 or whatever it may be, I never know what that means. Is it July? June? August even? I have no idea, and I always have to ask for dates anyway, or look at a calendar, because I can't figure it out in my head.

Week 9 is the only week I know "by heart", for this reason. All other weeks I can only relate to by looking in the calendar.

A common way at Volvo Cars is to write and talk about dates in this way; week two day three, or 20wk02d3 or just 20w02d3.

Which would translate to Wednesday January 8th year 2020

It is useful for deadlines because you always now how many weeks it is left.

It’s the first thing I (Norwegian) turn on (or miss) in calendar implementations. Most things are based on week number here too.

I'm British, but have been working with Norwegian companies for many years, and while it took a while, week numbers now feel very natural.

For those in English locales, Outlook has an option to enable week numbers in calendar views, and mobile calendar apps have this option too (at least the ones I've used).

Ditto for Denmark.

Used to have an .ics laying around for that purpose.

Could this be the one of the reasons ISO week dating was chosen as the format for Minecraft snapshots?