Format date of column headers after pivoting

Hello freelensia 

column headers have to be unique. So why not using weeks instead of months? Here an example

let
    Source = Table.FromRows(Json.Document(Binary.Decompress(Binary.FromText("TczBDcAgDEPRXXxGyEkoPXeH3lD2XwNQq4Sb9WT9MfC8KKBWWlWuKfDyq/RQTVULtVRjaEvlKrRPr6NrW2VrP7qM7w33CQ==", BinaryEncoding.Base64), Compression.Deflate)), let _t = ((type nullable text) meta [Serialized.Text = true]) in type table [Country = _t, Date = _t, Value = _t]),
    #"Changed Type" = Table.TransformColumnTypes(Source,{{"Country", type text}, {"Date", type date}, {"Value", Int64.Type}}, "de-DE"),
    #"Calculated Week of Year" = Table.TransformColumns(#"Changed Type",{{"Date", each Text.From(Date.WeekOfYear(_))&"/"&Text.From(Date.Year(_)), type text}}),
    #"Pivoted Column" = Table.Pivot(#"Calculated Week of Year", List.Distinct(#"Calculated Week of Year"[Date]), "Date", "Value", List.Sum)
in
    #"Pivoted Column"

Copy paste this code to the advanced editor in a new blank query to see how the solution works.

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Jimmy