UPDATE 2021-12-21: Since this post is about a year old, no one will see this update. However, I am happy to report my Pixel phone, which is on Android 12, displays ISO week # correctly, while my Samsung tablet, still on Android 11, still has this problem that ISO week numbering can not be specified in US English locale.

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Just discovered this year that Google Calendar can display week numbers. Now as we approach week 53, I see that it is correct on my desktop (Windows 10) and uses ISO 8601 week numbering. On my Android (11) phone, it appears that the week numbers are based on "week containing Jan 1 = week 1," so 2020 only has 52 weeks and 2021week numbers start a week early.

In both cases regional setting is US English, but week starting on Monday. For 2021, the week numbers differ by 1 all year as Jan 1 and Jan 4 are in different weeks. (Anybody know of a fix?)