Group dates by week where Monday is first day of week

[meileetan]

I have a column of dates. I see I can transform that column by Start of Week but how do I specify that Monday is the first day, instead of the default Sunday?

= Table.TransformColumns(#"Renamed Columns",{{"Week", Date.StartOfWeek, type date}})

 

[JGordon11]

= Table.TransformColumns(#"Renamed Columns",{{"Week", each Date.AddDays(Date.StartOfWeek(_),1), type date}})

 

[meileetan]

= Table.TransformColumns(#"Renamed Columns",{{"Week", each Date.AddDays(Date.StartOfWeek(_),1), type date}})

Ooh! Very close I originally thought your solution worked but then realised: it's marking Sunday 13 Feb 2022 in my new "Week starting" column as Monday 14 Feb. My desired outcome is for Sunday 13 Feb to fall in week starting 7 Feb.

 

[JGordon11]

If you use -1 instead of 1 does it produce the result you're after?

 

[meileetan]

= Table.TransformColumns(#"Renamed Columns",{{"Week", each Date.AddDays(Date.StartOfWeek(_),-1), type date}})

If you use -1 instead of 1 does it produce the result you're after?

For dates 6-11 Feb, the Week Starting date is 5 Feb.
I expect 6 Feb to be in Week Starting 31 Jan
And 7-11 Feb to be in Week Starting 7 Feb

 

[JGordon11]

maybe

= Table.TransformColumns(#"Renamed Columns",{{"Date", each Date.AddDays(Date.StartOfWeek(Date.AddDays(_,-1)),1), type date}})

 

[meileetan]

maybe

= Table.TransformColumns(#"Renamed Columns",{{"Date", each Date.AddDays(Date.StartOfWeek(Date.AddDays(_,-1)),1), type date}})

Works!
In parallel, a colleague shared this, which I think is neater. I really appreciate your help anyway!
1. Add Custom column
2. Type formula: =Date.StartOfWeek([Date],Day.Monday)
Where the underlined "Date" is the column you are referring to, to return the "Week starting on" value.