B4J Question Problem POI with dates from excel

Sub GetFormattedCellValue(workbook As XLWorkbookWriter, cell As PoiCell)

    Dim props As Map
    props.Initialize

    Dim val As String = cell.Value.As(String)
    XLgetCellStyleInfo(workbook, props, cell.CellStyle)
    Select Case props.GetDefault("setDataFormat", 0).As(Int) ' See https://poi.apache.org/apidocs/dev/org/apache/poi/ss/usermodel/BuiltinFormats.html
        Case 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 37, 38, 39, 40, 41, 42, 43, 44
            ' Numbers with or without decimals
        Case 11, 48
            ' Float
        Case 14, 15, 16, 17, 169 ' 169: not documented on the aforementioned page, found it experimentally
            ' Date
            Log("Date: " & DateToDDMMYYYYwithSlashes(val.As(Long)))
        Case 18, 19, 20, 21, 45, 46, 47
            ' Time
        Case 22
            ' Datetime
            Log("Date: " & DateToDDMMYYYYwithSlashes(val.As(Long)))
        Case Else
            ' Text
    End Select

    xui.MsgboxAsync("Hello World!", "B4X")

End Sub

'Call as:
'Dim props as Map
'Dim Cell As PoiCell
'XLgetCellStyleInfo(props, Cell.CellStyle)
Public Sub XLgetCellStyleInfo(workBook As XLWorkbookWriter, props As Map, CellStyle As PoiCellStyle)

    ' Code from XLUtils.b4xlib/XLSheetWriter.bas - see https://www.b4x.com/android/forum/threads/xlutils-jpoi-5-read-styles.140554

    Dim jStyle As JavaObject = CellStyle
    For Each methods As List In workBook.InternalAllSimpleMethods
        For Each method As String In methods
            props.Put(method, jStyle.RunMethod("g" & method.SubString(1), Null))
        Next
    Next
    props.Put("setFont", jStyle.RunMethod("getFontIndex", Null))
    For Each method As String In workBook.InternalStyleStrings
        props.Put(method, jStyle.RunMethodJO("g" & method.SubString(1), Null).RunMethod("toString", Null))
    Next

End Sub

Public Sub DateToDDMMYYYYwithSlashes(dateIn As Long) As String

    Dim OrigFormat As String = DateTime.DateFormat 'save orig date format
    DateTime.DateFormat = "dd/MM/yyyy"
    Dim YYYYMMDDout As String = DateTime.Date(dateIn)
    DateTime.DateFormat = OrigFormat 'return to orig date format
    Return YYYYMMDDout

End Sub