VBA Date Format For Variable - excel

Question

I need to turn content in a spreadsheet column from text to a date.
The cell format is text and the inputters were instructed to input a date as "ddmmyyyy".
Accidents happened and I found some content that would not parse as a date, including entries like "Unknown".
So I used a variable declared as a date and wrote an error handler to deal with content that would not parse.
Now for the bit I cannot work out.
If the date was 3rd March 2000 and someone input that as "03332000" that will not parse because "33" cannot be a month or a day; it is caught by the error handler as I wanted.
But if it was input as "03132000" I can't think of a way of preventing VBA converting that to a valid date as "13/03/2000".
Declaring a format for the date variable will not prevent VBA parsing the date.
I can write something that tests number range of the day and month part of the string but that is extra lines of code and I was hoping to do it just by the error handler.

Answer 1

I'd approach it a little differently and let Excel do the work.
Public Function ValidateDate(ByVal strDate As String) As Boolean
Dim intDay As Integer, intMonth As Integer, intYear As Integer, dtDate As Date
ValidateDate = True
On Error GoTo IsInValid
If Len(strDate) <> 8 Then GoTo IsInValid
If Not IsNumeric(strDate) Then GoTo IsInValid
intDay = Left(strDate, 2)
intMonth = Mid(strDate, 3, 2)
intYear = Right(strDate, 4)
dtDate = DateSerial(intYear, intMonth, intDay)
If DatePart("d", dtDate) <> intDay Then GoTo IsInValid
If DatePart("m", dtDate) <> intMonth Then GoTo IsInValid
If DatePart("yyyy", dtDate) <> intYear Then GoTo IsInValid
Exit Function
IsInValid:
ValidateDate = False
End Function
... this will ensure that anything related to leap years etc. will still work correctly and it will ensure that all entries are validated correctly.

Answer 2

If you place:
03332000
in cell A1 and run:
Sub CheckDate()
Dim s As String, d As Date
s = Range("A1").Text
d = DateSerial(CInt(Right(s, 4)), CInt(Mid(s, 3, 2)), CInt(Left(s, 2)))
MsgBox s & vbCrLf & d
End Sub
You will get:
So even though a valid month can only be in the range [1-12], Excel is trying to "help" you by interpreting the 33 as a projection of future date. For example, if the month was entered as 13, Excel will treat it as December of the following year!
You can't rely on error-handling for this. You need checks like:
Sub CheckDate2()
Dim s As String, d As Date
Dim dd As Integer, mm As Integer, yr As Integer
s = Range("A1").Text
yr = CInt(Right(s, 4))
mm = CInt(Mid(s, 3, 2))
dd = CInt(Left(s, 2))
If yr = 0 Or yr < 1900 Then
MsgBox "year is bad"
Exit Sub
End If
If dd = o Or dd > 31 Then
MsgBox "day is bad"
Exit Sub
End If
If mm = 0 Or mm > 12 Then
MsgBox "month is bad"
Exit Sub
End If
d = DateSerial(yr, mm, dd)
MsgBox s & vbCrLf & d
End Sub
You can also do other checks like looking at the length of the field, etc.