How to change week start from Sunday to Monday?

[SomeNoY]

Here’s the video: Imgur: The magic of the Internet.
Let’s say 26.01.25 is in week 4, since the week starts on Monday. But in Calc, using the WEEKNUM formula, it will display 5. How do I fix this?

[mikekaganski]

By reading WEEKNUM documentation and using the correct Mode argument, so that it uses Monday as the start of the week.