WEEKNUM() Discrepancy | Depends on your Locale

MultiTech
Participant V

While troubleshooting an issue with WEEKNUM(), I came across a curious fact that I thought I would share.

  • The internet, or at least the websites you’d go to for answers if you Googled something, don’t count the first incomplete week of the year when figuring week numbers.

    • Which means if you’re in the US (among a few other countries) and searched the internet to find out what week number it was…
      • the numbers would be wrong (from your perspective).

Assume that for this discussion, Sunday is the start of the week

  • Let’s work with the date: Sunday July 11th, 2021

In Google Sheets & AppSheet

  • WEEKNUM(“7/11/2021”) = 29

3X_c_8_c8e58dc01f8e6c85df3fbf1d2bac90ab7baff6a7.png

  • If you physically count the number of weeks on a calendar, you’ll get 29 too.
    • IF you count the first incomplete week, that is…

But On The Internet

  • WEEKNUM(“7/11/2021”) = 28

It seems that the internet doesn’t count the first incomplete week of the year

3X_2_4_24fc5b3b37dc8ec533a09880b35be7c9d078c0b1.png

Every webpage that I’ve gone to tells me that the week number for July 11th, 2021 is 28.
Check for yourself:

Examples

Some Results:

  • Week Numbers for 2021
  • This one starts the week on Monday, but still you see the next week is 28 - not 29.

  • https://weeknumber.com/
  • Another that starts it’s weeks on Monday - but still, the next week should be 29, not 28.

That’s 4 websites that I’ve given pictures from, but every website on the first two pages of results for that search give this answer


I don’t know about you, but I had no idea that this wasn’t a standard-across-the-world thing.


I’m curious what everyone thinks?

  • When should we start counting the first week of the year?
  • Start counting from the first FULL week
  • Start counting from the first DAY

0 voters

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2 REPLIES 2

I think defining which is first week of the year and so on is based on standards followed by different countries.

Most of Europe follows ISO standard week numbers and USA , Canada and some other countries follow a different system, a week starting on 1st January as first week.

It turns out something similar to date formats followed in different countries (mm/dd or dd/mm)

I think Google Sheets WEEKNUM() allows both options - ISO as well as the one followed by US.
https://support.google.com/docs/answer/3294949?hl=en

The articles below describe these week numbering systems.

https://www.calendar-12.com/week_number

Below are two interesting post threads on Weeknumbers. @Aleksi has suggested an interesting solution in one of the threads.

MultiTech
Participant V

I was just pointing out that if you live in the US and you Google, “What is the current weeknum?” you’ll get a (seemingly) wrong answer.

  • Yet another thing the US does differently than the world.
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