Sub test()
Dim LR1 as long, cell As Range
With ThisWorkbook.Sheets(1)
LR1 = .Range("A" & Rows.Count).End(xlUp).Row
For Each cell In .Range("D2:D" & LR1)
With cell
.Value = .Offset(, -3) & "/" & .Offset(, -2) & "/" & .Offset(, -1)
.Value = .Value
.NumberFormat = "dd/mm/yyyy"
End With
Next cell
End With
End Sub