WEEKNUM() Discrepancy | Depends on your Locale

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


  • 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


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


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

1 Like

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.

The articles below describe these week numbering systems.


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

1 Like

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. :roll_eyes:
1 Like