How to I check if a date is valid then reformat it?

[monkey288195]

I simply want to check if my strings are valid dates and then have them formatted. But "datecheck2 = IsDate(Month)" always returns as false.

                Dim datecheck As Boolean
                Dim yearMonth As String = yearandmonth ' currently looks like yyyy-MM
                Dim allowedFormat() As String = {"yyyy-MM"}
                Dim dd As DateTime
                datecheck = IsDate(yearMonth) ' returns true or false if date is valid. EX: 2017-13 = false because "13" is over 12                


                If datecheck = True Then ' if the date is valid I want it to be reformatted to "yyyy-MM"

                    DateTime.TryParseExact(yearMonth, allowedFormat, Globalization.CultureInfo.InvariantCulture, Globalization.DateTimeStyles.None, dd)
                    Dim yearMonthFormat As String = dd.ToString("yyyy-MM")
                   

                Else

                    MsgBox("Invalid year/month")

                End If




                Dim datecheck2 As Boolean
                Dim Month As String = filemonth ' string looks like this: "MM"
                Dim allowedFormat2() As String = {"MM - MMMM"}
                Dim dt As DateTime


                datecheck2 = IsDate(Month) ' THIS RETURNS FALSE FOR MONTH. Example: If Month = "05" then it returns false. Even though it is a valid month
                MsgBox(datecheck2)

                If datecheck2 = True Then
'this reformats it to "MM - MMMM"

                    DateTime.TryParseExact(Month, allowedFormat2, Globalization.CultureInfo.InvariantCulture, Globalization.DateTimeStyles.None, dt)
                    Dim monthFormat As String = dt.ToString("MM - MMMM")
                    MsgBox(monthFormat)
                Else

                    MsgBox("Invalid Month") ' change to log


                End If

edit: added comments to make code clear