Need Help Writing a Dated Difference Formula

Hi KarlConstruct ,

Sorry for our mistake, please try to use the follwing sub query, also very appreciate danextian  can point the error.

Test = Table.SelectRows(
    #"Changed Type2",
    each let d = [Sent Date],
             n = [Submittal ID],
             t = Table.SelectRows(#"Changed Type2", each [Submittal ID]=n),
                 isMin = List.Contains(Table.ToList(Table.TransformColumnTypes(Table.SelectColumns(Record.ToTable(Table.Min(Table.SelectColumns(t,"Sent Date"),"Sent Date")),"Value"),{{"Value",type text}})),Date.ToText(d)),
                 isMax = List.Contains(Table.ToList(Table.TransformColumnTypes(Table.SelectColumns(Record.ToTable(Table.Max(Table.SelectColumns(t,"Sent Date"),"Sent Date")),"Value"),{{"Value",type text}})),Date.ToText(d))
         in 
             isMin or isMax
)

We do not need to change the type of Submittal ID column, the Value is the column name of record.

All the queries are here:

let
    Source = Table.FromRows(Json.Document(Binary.Decompress(Binary.FromText("Zc65DcAgEADBXi4G6R7eWhD9t2HLThCbTjRriUkSV5tZLavLThcFqZAqqX3kJ3XSIE2QKclI/z5OClIhVVIjddK73w8=", BinaryEncoding.Base64), Compression.Deflate)), let _t = ((type text) meta [Serialized.Text = true]) in type table [#"Submittal ID" = _t, #"Sent Date" = _t]),
    #"Changed Type2" = Table.TransformColumnTypes(Source,{{"Submittal ID", type number}, {"Sent Date", type date}}),
    Test = Table.SelectRows(
    #"Changed Type2",
    each let d = [Sent Date],
             n = [Submittal ID],
             t = Table.SelectRows(#"Changed Type2", each [Submittal ID]=n),
                 isMin = List.Contains(Table.ToList(Table.TransformColumnTypes(Table.SelectColumns(Record.ToTable(Table.Min(Table.SelectColumns(t,"Sent Date"),"Sent Date")),"Value"),{{"Value",type text}})),Date.ToText(d)),
                 isMax = List.Contains(Table.ToList(Table.TransformColumnTypes(Table.SelectColumns(Record.ToTable(Table.Max(Table.SelectColumns(t,"Sent Date"),"Sent Date")),"Value"),{{"Value",type text}})),Date.ToText(d))
         in 
             isMin or isMax
)
in
    Test

Best regards,