Option Explicit
Sub European_US_Dates()
Dim rCell As Range, rRange As Range
Set rRange = Columns(1).SpecialCells(xlCellTypeConstants, xlNumbers)
For Each rCell In rRange
If IsDate(rCell) Then rCell(1, 2) = _
DateSerial(Year(rCell), Month(rCell), Day(rCell))
Next rCell
End Sub