BUG: ISOWEEKNUM is incorrect for 2023

I have discovered that according to the formula function ISOWEEKNUM, Monday, Jan 2, 2023 is ISO week 52 (2022) and Monday, Jan 9, 2023 is in ISO week 1 (2023). Tuesday, January 3, 2023 is showing week 1.

Here is a list of the 2023 ISO weeks: 2023 ISO WEEKS or another one.

I have been unable to find any source that contradicts that Monday, January 2nd 2023 is ISO week 1, not week 52 (of 2022) like the function returns.

Weird, on my account the formula shows week 1 (correct) as the week column shows week 1 (correct

is the formula ISOWEEKNUM({Date}) in yours? Interestingly, if the time is turned on for the Date column it WORKS CORRECTLY. But turn the time off, and it breaks. For me.

Correct, using the formula ISOWEEKNUM({Date}). Maybe related, my monday.com are:


My date column has no time added to it.

I wish it were so simple. I’ve tried those settings as well as time zone, 12/24H etc. in my account profile.

The only thing left to investigate is changing localization on my operating system in case for some reason it’s relying on machine localization for something and my being on the opposite side of Greenwich is causing issues until I turn on the time display. Not doing that at 2am.

@basdebruin I can confirm the issue is related to operating system time zone settings. The issue only occurs if the timezone setting is behind UTC. If its UTC or ahead of UTC then it behaves as expected.