Public Class frmCheckDateTime
 
    'Für die Auswahl der Zeitintervalle
    Dim dt As New DataTable
    Dim bs As New BindingSource
    Dim dgv As New DataGridView With _
        {.Parent = Me, .DataSource = bs, .Width = 300, .ReadOnly = true}
 
    'Controls für Eingabe des zu prüfenden Zeitpunktes
    Dim datepicker As New DateTimePicker With _
      {.Parent = Me, .Left = 320, .Width = 100, _
       .Format = DateTimePickerFormat.Short}
 
    Dim timepicker As New DateTimePicker With _
        {.Parent = Me, .Left = 430, .Width = 100, _
         .Format = DateTimePickerFormat.Time, .ShowUpDown = True}
 
    'Für die Prüfung des Zeitpunktes
    Dim WithEvents btnCheck As New Button With _
        {.Parent = Me, .Left = 320, .Width = 100, .Top = 100, .Text = "Check"}
 
 
    Private Sub frmCheckDateTime_Load(sender As System.Object, _
        e As System.EventArgs) Handles MyBase.Load
 
        Me.Width = 550
        Me.Height = 500
 
        'Liste der wählbaren Zeitintervalle in die Datatable eintragen
        dt.Columns.Add("Weekday", GetType(String))
        dt.Columns.Add("StartTime", GetType(String))
 
        Dim wd As String = GetWeekday(Now)
        For i As Integer = 1 To 7
            Dim wdn As String = _
                DateAndTime.WeekdayName(i, False, FirstDayOfWeek.Monday)
            For hr As Integer = 0 To 23
                dt.Rows.Add(wdn, hr.ToString & ":00")
                dt.Rows.Add(wdn, hr.ToString & ":30")
            Next hr
        Next i
 
        bs.DataSource = dt
    End Sub
 
 
    Private Function GetWeekday(ByVal dtim As DateTime) As String
        Return dtim.ToString("dddd", Globalization.CultureInfo.CurrentCulture)
    End Function
 
 
    Private Function IsIntime(ByVal r As DataRow, dtim As DateTime) As Boolean
 
        'Liegt dtim im Zeitintervall, das in r eingetragen ist ??
        Dim wdn As String = GetWeekday(dtim)
        If Not wdn = r("Weekday").ToString Then Return False
 
        Dim rhour As Integer = CInt(r("StartTime").ToString.Split(":"c)(0))
        Dim rmin As Integer = CInt(r("StartTime").ToString.Split(":"c)(1))
 
        If Not dtim.Hour = rhour Then Return False
        If dtim.Minute < 30 AndAlso rmin = 30 Then Return False
        If dtim.Minute >= 30 AndAlso rmin = 0 Then Return False
        Return True
    End Function
 
 
    Private Function CheckDateTime(ByVal dtim As DateTime) As Boolean
 
        For i As Integer = 0 To bs.Count - 1
            If dgv.Rows(i).Selected Then
                'Ein gewähltes Zeitintervall checken
                If IsIntime(DirectCast(bs(i), DataRowView).Row, dtim) _
                   Then Return True
            End If
        Next i
        Return False
    End Function
 
 
    Private Sub btnCheck_Click(sender As Object, _
        e As System.EventArgs) Handles btnCheck.Click
 
        'Gewähltes Datum und und gewählte Uhrzeit zusammenfügen
        Dim dtim As DateTime = datepicker.Value.Date
        dtim = dtim.AddHours(timepicker.Value.Hour)
        dtim = dtim.AddMinutes(timepicker.Value.Minute)
 
        If CheckDateTime(dtim) Then
            MsgBox("Zeitpunkt liegt in einem gewählten Intervall")
        Else
            MsgBox("Zeitpunkt liegt nicht in einem gewählten Intervall")
        End If
    End Sub
End Class