Date Validation not working correctly - vba

Question

I am trying to validate a date that is entered into a textbox on a user form. When I enter for example 23/7/15 the code works fine and gives me a value as the date entered is valid, when I enter 32/7/2015 I get a message that I program telling the user that they have entered a wrong date but if I enter 32/7/15 it sets the date in the code to some date in 1932 and as this is a valid date it does not throw the error. Below is the code that I am using. Is there anyway to validate 32/7/15?
Private Function errorCheckingDate(box1, message) As Boolean '<============= Returns a True or a False
If Not IsDate(box1) Then '<============================================= Checks to see if entered value is date or not
MsgBox message, vbExclamation, "Invalid Selection" '<=============== Displays a messgae box if not date
box1.SetFocus '<==================================================== Puts cursor back to the offending box
errorCheckingDate = True '<========================================= Sets function to True
End If
End Function
box1 is just the value of the textbox once it has been converted to a date. Below is the conversion
secondSelectedStr = Format(DateTextBox.value, "dd-mm-yy") '<===== Convert to correct format
Any help would be great.

Answer 1

In addition to the ordering issue, VBA will also try to adapt invalid date ranges to a proper date. For example, this has always been a neat technique to get the X day of the year:
d = DateSerial(2015, 1, X)
X can be really any number here (up to the limits of the data type, of course). If X is 500, it will produce the date 2016-5-14. So the mm/dd vs dd/mm vs yy/mm/dd issue plus the fact that VBA accepts numbers outside valid ranges are both troublesome.
Without range-checking each date component (where you have to consider leap years and whatnot), I think the best solution is to just have VBA create your date and then test it to ensure it's what you're expecting. For example:
' Get the date components (assuming d/m/yy)...
Dim a As Variant
a = Split(strDate, "/")
' Need 3 components...
If UBound(a) <> 2 Then MsgBox "Invalid date": Exit Sub
' Create the date. This will hardly ever fail.
' VBA will create some kind of date using whatever numbers you throw at it.
Dim d As Date
d = DateSerial(a(2), a(1), a(0))
' Make sure the date VBA created matches what we expected...
If Day(d) <> CInt(a(0)) Then MsgBox "Invalid day": Exit Sub
If Month(d) <> CInt(a(1)) Then MsgBox "Invalid month": Exit Sub
If Right$(Year(d), 2) <> a(2) Then MsgBox "Invalid year": Exit Sub
You could throw that into a subroutine (you may have noticed the Exit Sub statements) to validate the date that gets entered. The TextBox_Exit event would work well. That way, you could set Cancel = True to prevent the user from leaving the textbox with an invalid date.

Answer 2

Thanks for the answers guys but I need to accommodate for leap years and other things. As the isdate function works if the date is entered in the form 1/1/2015 I have just used the len() function to make sure that the date entered is of a certain length. Below is the code that I used. Thanks for you help once again. :)
Private Function errorCheckingDate(box1, message) As Boolean '<============= Returns a True or a False
If Not IsDate(box1) Or Len(box1) < 8 Or Len(box1) > 10 Then '<============================================= Checks to see if entered value is date or not
MsgBox message, vbExclamation, "Invalid Selection" '<=============== Displays a messgae box if not date
box1.SetFocus '<==================================================== Puts cursor back to the offending box
errorCheckingDate = True '<========================================= Sets function to True
End If
End Function

Answer 3

Maybe instead of using IsDate you could use your own custom function likened to it.
Function isValidDate(d as String) as Boolean
Dim parts as Variant
Dim months29 as variant
Dim months30 as variant
Dim months31 as variant
months29 = Array(2)
months30 = Array(4, 6, 9, 11)
months31 = Array(1, 3, 5, 7, 8, 10, 12)
parts = Split(d, "-")
if parts(2) mod 4 = 0 then
daysLeapYear = 28
else:
daysLeapYear = 29
end if
if ((IsInArray(parts(0), months29) and parts(1) <= daysLeapYear) or _
(IsInArray(parts(0), months30) and parts(1) < 31) or _
(IsInArray(parts(0), months31) and parts(1) < 32)) and _
parts(2) < 16 then
isValidDate = True
else:
isValidDate = False
end if
end function
Function IsInArray(stringToBeFound As String, arr As Variant) As Boolean
IsInArray = (UBound(Filter(arr, stringToBeFound)) > -1)
End Function
This should cover most cases. Not sure how detailed you feel you need to be. IsInArray courtesy of #JimmyPena.