''' <summary>Prüft, ob ein Zeitpunkt innerhalb eines Zeitintervals liegt</summary>
''' <param name="DateTimeToCheck">zu prüfender Zeitpunkt</param>
''' <param name="LowerLimit">Beginn des Zeitintervalls</param>
''' <param name="UpperLimit">Ende des Zeitintervalls</param>
''' <param name="IncludeDate">Soll das Datum einbezogen werden?</param>
''' <param name="IncludeLowerLimit">Liegt der Beginn im Zeitintervall?</param>
''' <param name="IncludeUpperLimit">Liegt das Ende noch im Zeitintervall?</param>
''' <param name="AllowDateChange">
''' Ist ein Tageswechsel zwischen den Uhrzeiten erlaubt?</param>
    Private Function IsInTimeInterval(ByVal DateTimeToCheck As DateTime, _
        ByVal LowerLimit As DateTime, ByVal UpperLimit As DateTime, _
        Optional ByVal IncludeDate As Boolean = False, _
        Optional ByVal IncludeLowerLimit As Boolean = True, _
        Optional ByVal IncludeUpperLimit As Boolean = True, _
        Optional ByVal AllowDateChange As Boolean = False) As Boolean
 
        Dim basedate As New DateTime(2000, 1, 1)
 
        If Not IncludeDate Then
            UpperLimit = basedate.Add(UpperLimit.TimeOfDay)
            LowerLimit = basedate.Add(LowerLimit.TimeOfDay)
            DateTimeToCheck = basedate.Add(DateTimeToCheck.TimeOfDay)
        End If
 
        If LowerLimit > UpperLimit Then
            If Not IncludeDate AndAlso AllowDateChange Then
                'Tageswechsel zwischen den beiden Uhrzeiten 
                UpperLimit = UpperLimit.AddDays(1)
            Else
                Throw New ArgumentException _
                    ("Unzulässige Angabe für Zeitfenster")
            End If
        End If
 
        Dim CheckUpper, CheckLower As Boolean
        If IncludeLowerLimit Then
            CheckLower = DateTimeToCheck >= LowerLimit
        Else
            CheckLower = DateTimeToCheck > LowerLimit
        End If
        If IncludeUpperLimit Then
            CheckUpper = DateTimeToCheck <= UpperLimit
        Else
            CheckUpper = DateTimeToCheck < UpperLimit
        End If
 
        Return CheckUpper And CheckLower
    End Function