let
    Source =
        Excel.CurrentWorkbook(){[Name="Таблица1"]}[Content],
    Filtered =
        Table.SelectRows(Source, each ([Номер акта] <> null)),
    Typed =
        Table.TransformColumnTypes(
            Filtered,
            {
                {"дата начала", Int64.Type},
                {"дата окончания", Int64.Type},
                {"дата акта", type date},
                {"кол-во экз", Int64.Type},
                {"Номер п/п", Int64.Type}}
        ),
    Combined =
        Table.CombineColumns(
            Typed,
            {"дата начала", "дата окончания"},
            each {_{0}.._{1}},
            "Даты"
        ),
    Expand =
        Table.ExpandListColumn(Combined, "Даты"),
    Typed1 =
        Table.TransformColumnTypes(Expand,{{"Даты", type date}})
in
    Typed1