Need Help Writing a Dated Difference Formula

Hi KarlConstruct ,

We can filter the rows of first date and the last date in power query editor if you need.

let
    Source = Table.FromRows(Json.Document(Binary.Decompress(Binary.FromText("Zc67DcAgDEDBXVyDZPMNZcIYiP3XSAQNymuvujHkFidBrXk1r0Gm+1EkJVImlUXPSZV0kRrIlGSkve8nRVIiZVIhVdK3ny8=", BinaryEncoding.Base64), Compression.Deflate)), let _t = ((type text) meta [Serialized.Text = true]) in type table [Name = _t, Date = _t]),
    #"Changed Type" = Table.TransformColumnTypes(Source,{{"Name", type text}, {"Date", type date}}),
    Test = Table.SelectRows(
                #"Changed Type",
                each let d = [Date],
                         n = [Name],
                         t = Table.SelectRows(#"Changed Type", each [Name]=n),
                         isMin = List.Contains(Table.ToList(Table.TransformColumnTypes(Table.SelectColumns(Record.ToTable(Table.Min(Table.SelectColumns(t,"Date"),"Date")),"Value"),{{"Value",type text}})),Date.ToText(d)),
                         isMax = List.Contains(Table.ToList(Table.TransformColumnTypes(Table.SelectColumns(Record.ToTable(Table.Max(Table.SelectColumns(t,"Date"),"Date")),"Value"),{{"Value",type text}})),Date.ToText(d))
                      in 
                        isMin or isMax
            )
in
    Test

The formula may need to do some change based on the type and name of columns.

BTW, pbix as attached.

Best regards,

Community Support Team _ Dong Li
If this post helps, then please consider Accept it as the solution to help the other members find it more quickly.