VBA Regular Expression to Match Date - regex

Question

I'm new to Regular Expressions and am having difficulty getting patterns that I find online to work in VBScript/VBA. This one is supposed to return a date found in a string but it fails to find any dates. What does VBScript/VBA do different than other RegEx engines that makes this fail to return a match?
Edit1
I removed the ^ and the $ from my pattern. The problem persists.
Private Sub TestDate()
MsgBox RegExDate("cancel on 12/21/2010 ")
End Sub
Private Function RegExDate(s As String) As String
Dim re, match
Set re = CreateObject("vbscript.regexp")
re.Pattern = "(((0[1-9]|[12]\d|3[01])\/(0[13578]|1[02])\/((19|[2-9]\d)\d{2}))|((0[1-9]|[12]\d|30)\/(0[13456789]|1[012])\/((19|[2-9]\d)\d{2}))|((0[1-9]|1\d|2[0-8])\/02\/((19|[2-9]\d)\d{2}))|(29\/02\/((1[6-9]|[2-9]\d)(0[48]|[2468][048]|[13579][26])|((16|[2468][048]|[3579][26])00))))"
re.Global = True
For Each match In re.Execute(s)
MsgBox match.value
RegExDate = match.value
Exit For
Next
Set re = Nothing
End Function

Answer 1

It looks as if your RegEx will only find match if the whole string you pass to it is a date.
Try removing ^ and $
Here's your example reworked using a RegEx that will find dates in the mm/dd/yyyy and mm-dd-yyyy formats -
Private Sub TestDate()
MsgBox RegExDate("cancel on 12/21/2010 ")
End Sub
Private Function RegExDate(s As String) As String
Dim re, match
Set re = CreateObject("vbscript.regexp")
re.Pattern = "(0[1-9]|1[012])[- /.](0[1-9]|[12][0-9]|3[01])[- /.](19|20)[0-9]{2}"
re.Global = True
For Each match In re.Execute(s)
MsgBox match.Value
RegExDate = match.Value
Exit For
Next
Set re = Nothing
End Function

Answer 2

Why not use RegEx to get the portion of the string that appears to be the date and use the IsDate Function to validate it?
Function FormatOutput(s)
Dim re, match
Set re = CreateObject("vbscript.regexp")
re.Pattern = "[\d]+[\/-][\d]+[\/-][\d]+"
re.Global = True
For Each match In re.Execute(s)
if IsDate(match.value) then
FormatOutput = CDate(match.value)
Exit For
end if
Next
Set re = Nothing
End Function
The RegEx could be cleared up a bit, but it works for your current example.