Excel macro date parser cannot handle single-digit days

From previous questions on this and other sites I was given a function that can parse for and find dates in text strings or cells. Here's the function:

Function GetDate(strInput As String) As Date
    Dim DateFormat() As String
    Dim intDateLength As Integer
    Dim intMaxFormat As Integer
    Dim intFrmtCtr As Integer
    Dim intPosition As Integer
    intMaxFormat = 6
    ReDim DateFormat(1 To intMaxFormat)
    DateFormat(1) = "*##[-/]##[/-]####*"
    DateFormat(2) = "*#[-/]##[-/]####*"
    DateFormat(3) = "*##[-/]#[-/]####*"
    DateFormat(4) = "*##[-/]##[-/]##*"
    DateFormat(5) = "*#[-/]##[-/]##*"
    DateFormat(6) = "*#[-/]#[-/]##*"
    GetDate = Now
    For intFrmtCtr = 1 To intMaxFormat
        If strInput Like DateFormat(intFrmtCtr) Then
            intDateLength = Len(DateFormat(intFrmtCtr)) - 8
            strInput = Replace(strInput, " ", "")
            For intPosition = 1 To Len(strInput)
                If Mid(strInput, intPosition, intDateLength) Like DateFormat(intFrmtCtr) Then
                    GetDate = DateValue(Mid(strInput, intPosition, intDateLength))
                    Exit Function
                End If
            Next intPosition
        End If
    Next intFrmtCtr
End Function

This is then called by referencing a cell address:

'Gets date from cell A2
    Range("A2").Select
    dateWork = GetDate(Selection)

I can then format the output using Format(dateWork, "mmddyy") or similar.

In the case above, given a cell contents of 8/31/2011 the string 08312011 is returned.

Beginning with cell content dates with a single digit day (ie, early in the month), though, the function began returning the first two digits of the year instead of the second two digits. All of a sudden, dates started looking like they were in 2020, not 2011.

I've been able to test this using otherwise identical input data sheets where dates up to and including 8/31/2011 were returned correctly and dates beginning with 9/1/2011 and continuing all return "20" as the year.

Where is this function breaking down?

UPDATE clarification for questions:

I use this function in several macros acting upon data exported from a report-generating tool (Business Objects). It is possible to manually edit the date in the input files, but that rather defeats the purpose of the macros and so should not be considered an option.

The GetDate() function can be called upon to find dates in any string. The strings can be just the date in any of various formats, or they can be combinations of text and date such as "Totals as of 9/13/1977".

I would appreciate your simplification or edits to the function so long as it retains the abilities laid out above.

Answer

Your Mid(strInput, intPosition, intDateLength) isn't working for you. For 9/1/2011, you're matching DateFormat(6) = "*#[-/]#[-/]##*". So Mid(strInput, intPosition, intDateLength) = Mid("9/1/2011", 1, 6) and returns "9/1/20" rather than "9/1/2011".

based on your example above, I think you need to add 2 more patterns so that you cover all combinations of 1 and 2 digit months/days & 2 and 4 digit years. Order is important because you want to match the 4 digit years first (noting that the reason you have a problem is that #/#/## matches 9/1/2011 when in fact you only want it to match 9/1/11. So the code change is something like the below. I haven't exhaustively tested it with all date formats, but it seems OK.

intMaxFormat = 8
ReDim DateFormat(1 To intMaxFormat)
DateFormat(1) = "*##[-/]##[/-]####*"
DateFormat(2) = "*#[-/]##[-/]####*"
DateFormat(3) = "*##[-/]#[-/]####*"
DateFormat(4) = "*#[-/]#[-/]####*"
DateFormat(5) = "*##[-/]##[-/]##*"
DateFormat(6) = "*##[-/]#[-/]##*"
DateFormat(7) = "*#[-/]##[-/]##*"
DateFormat(8) = "*#[-/]#[-/]##*"