Public Class frmMonthCalendarDemo
 
    Dim mc As New MonthCalendar With {.Parent = Me, .Size = New Size(400, 400)}
 
 
    Private Sub frmMonthCalendarDemo_Load(sender As Object, e As EventArgs) _
      Handles MyBase.Load
 
        'Eine Beispieltabelle 
        Dim dt As New DataTable
        dt.Columns.Add("Datum_Von", GetType(DateTime))
        dt.Columns.Add("Datum_bis", GetType(DateTime))
        'Zwei Zeitspannen
        dt.Rows.Add({New Date(2024, 1, 1), New Date(2024, 1, 7)})
        dt.Rows.Add({New Date(2024, 1, 13), New Date(2024, 1, 19)})
        dt.Rows.Add({Nothing, New Date(2024, 1, 31)})
 
        Dim d As DateTime
 
        For r As Integer = 0 To dt.Rows.Count - 1
            If Not IsDBNull(dt.Rows(r)("Datum_von")) _
               AndAlso Not IsDBNull(dt.Rows(r)("Datum_Bis")) Then
 
                d = CType(dt.Rows(r)("Datum_von"), DateTime).Date
                'Tagesschleife über die Zeitspanne
                Do
                    mc.AddBoldedDate(d)
                    d = d.AddDays(1)
                Loop While d <= CType(dt.Rows(r)("Datum_bis"), DateTime).Date
            End If
 
        Next r
 
        mc.UpdateBoldedDates()
    End Sub
End Class