If you are looking for the Excel equivalent of the WEEKNUM function for Power Query this article is for you.
As this is also a function that has many regional options, I was lucky to find an algorithm that I could use for its main part here: M functions to convert between ISO 8601 Week & Year ⇄ dates (e.g., 2014-12-29 ⇄ "2015-W01-1") (github.com)
Excel WEEKNUM function for Power Query
https://gist.github.com/ImkeF/29797a686e57aebb742c7a506df632f1
Function parameters
The function takes the same parameters as its Excel equivalent. So this is just a copy for your convenient reference:
WEEKNUM(serial_number,[return_type])
The WEEKNUM function syntax has the following arguments:
- Serial_number Required. A date within the week. Dates should be entered by using the DATE function, or as results of other formulas or functions. For example, use DATE(2008,5,23) for the 23rd day of May, 2008. Problems can occur if dates are entered as text.
- Return_type Optional. A number that determines on which day the week begins. The default is 1.
| Return_type | Week begins on | System |
|---|---|---|
| 1 or omitted | Sunday | 1 |
| 2 | Monday | 1 |
| 11 | Monday | 1 |
| 12 | Tuesday | 1 |
| 13 | Wednesday | 1 |
| 14 | Thursday | 1 |
| 15 | Friday | 1 |
| 16 | Saturday | 1 |
| 17 | Sunday | 1 |
| 21 | Monday | 2 |
If you are interested in more Power Query functions that replicate Excel functions who haven’t made it into the M-language (yet?) please check out this collection.
Enjoy and stay queryious 😉
Hello
I want to share with you my own ISO week number function
(d as date) =>
let
Week_Thursday = Date.AddDays(d,3-Date.DayOfWeek(d,Day.Monday)),
Week_Year =Date.Year(Week_Thursday),Year_First_Thursday = Date.AddDays(#date(Week_Year,1,7),-Date.DayOfWeek(#date(Week_Year,1,1),Day.Friday)),
Week_Num = Duration.Days(Week_Thursday - Year_First_Thursday)/7+1
in
Week_Num
//For 2022-W04 : Text.From(Week_Year)&”-W”&Text.PadStart(Text.From(Week_Num),2,”0″)