Date data changing from custom to general in a single column

Hello osabhaois 

check out this solution with Table.TransformColumns

let
    Source = Table.FromRows(Json.Document(Binary.Decompress(Binary.FromText("i45WMjTQNzDUNzIwMlAwMLYyNVCK1YlWUrDUNzaACBqagAVjAQ==", BinaryEncoding.Base64), Compression.Deflate)), let _t = ((type nullable text) meta [Serialized.Text = true]) in type table [Column1 = _t]),
    Transform = Table.TransformColumns
    (
        Source,
        {
            {
                "Column1",
                each DateTime.From(_,"en-US"),
                type datetime
            }
        }
    )
in
    Transform

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

If this post helps or solves your problem, please mark it as solution (to help other users find useful content and to acknowledge the work of users that helped you)
Kudoes are nice too

Have fun

Jimmy