Nerdsniping of the day (I was the victim): Are there years when the US vs ISO abiding countries do not agree on the week number?
The answer as per playing a bit with python is: yes indeed, and 2027 will be the next occurrence. On this date 2 years from now, the US is living week 15 while most of us are still in week 14.
The root cause is a different definition of week 1, whether it's placed on January 1st or January 4th.
In addition there's the bit where we disagree on the number every Sunday and other Fun conflicts I'm omitting for brevity, but that's mostly small potatoes to almost an entire year of potential misunderstandings!