VBA/Excel は、しばしば日付を決定しようとし、それを間違えます。
例えば
dt = DateSerial(2012, 14, 42) 'returns #14/03/2013#
dtReal = IsDate("09 / 14 / 2012") 'returns TRUE when we really wanted to test dd/mm/yyyy - there's no 14th month.
私はよく以下のコードを使用します。これは、文字列の日付が本物かどうかを判断し、日付として返す、より長くても確実な方法です。
Option Explicit
Sub test()
Dim testDate As Boolean
Dim dt As Date
testDate = IsTextDate("05/07/2012", dt, "dd/mm/yyyy") 'Could pass "mm/dd/yyyy" instead
If testDate = True Then
Debug.Print "Valid Date " & Format(dt, "dd-mmm-yyyy")
Else
Debug.Print "Invalid Date"
End If
End Sub
Function IsTextDate(ByVal str As String, ByRef dt As Date, Optional dtFormat As String = "dd/mm/yyyy") As Boolean
Dim D As Date
Dim day As Integer
Dim month As Integer
Dim year As Long
Dim daysinFeb As Integer
Dim dtArray() As String
'Test input string mask matches date format
If Not (str Like "##/##/####") Then
'Debug.Print "Invalid Date"
Exit Function
Else
'split string on delimiter and extract correct 'dd' and 'mm' based on UK/US format
dtArray = Split(str, "/")
year = CInt(dtArray(2))
If dtFormat = "dd/mm/yyyy" Then
day = CInt(dtArray(0))
month = CInt(dtArray(1))
Else
day = CInt(dtArray(1))
month = CInt(dtArray(0))
End If
'determine days in Feb for year given.
If IsDate("2/29/" & year) Then
daysinFeb = 29
Else
daysinFeb = 28
End If
'determine if date is valid
Select Case month
Case 9, 4, 6, 11
'30 days
If day <= 30 Then IsTextDate = True
Case 1, 3, 5, 7, 8, 10, 12
'31 days
If day <= 31 Then IsTextDate = True
Case 2
'either 28 or 19 days
If day <= daysinFeb Then IsTextDate = True
End Select
If IsTextDate Then dt = DateSerial(year, month, day)
End If
End Function