Speed up excel formatting vba code?

Question

I am using the following vba code to change a text string date into an actual date in excel so I can use it for logical comparisons and the like.

The problem is I need t

Answer 1

First steps would be:

• Turn screen updating off
• Turn calculation off
• Read and write the range at once

It could look like the code below - it is a good idea to include an error handler to avoid leaving your spreadsheet with screen updates off or with the calculation mode changed:

Sub Datechange()

    On Error GoTo error_handler

    Dim initialMode As Long

    initialMode = Application.Calculation 'save calculation mode
    Application.Calculation = xlCalculationManual 'turn calculation to manual
    Application.ScreenUpdating = False 'turn off screen updating

    Dim data As Variant
    Dim i As Long

    'copy range to an array
    data = Range("D2:D" & Range("D" & Rows.Count).End(xlUp).Row)

    For i = LBound(data, 1) To UBound(data, 1)
        'modify the array if the value looks like a date, else skip it
        If IsDate(data(i, 1)) Then data(i, 1) = CDate(data(i, 1))
    Next i

    'copy array back to range
    Range("D2:D" & Range("D" & Rows.Count).End(xlUp).Row) = data

exit_door:
    Application.ScreenUpdating = True 'turn screen updating on
    Application.Calculation = initialMode 'restore original calculation mode

    Exit Sub

error_handler:
    'if there is an error, let the user know
    MsgBox "Error encountered on line " & i + 1 & ": " & Err.Description
    Resume exit_door 'don't forget the exit door to restore the calculation mode
End Sub