Option Explicit

Private Sub Form_Load()
  With MonthView1
    .Day = Day(Now)
    .Month = Month(Now)
    .Year = Year(Now)
  End With
End Sub

Private Sub MonthView1_DateClick(ByVal DateClicked As Date)
  Label1.Caption = " " & IstFeiertag(DateClicked)
End Sub

Private Sub MonthView1_SelChange(ByVal StartDate As Date, _
      ByVal EndDate As Date, Cancel As Boolean)
  MonthView1_DateClick StartDate
End Sub

Private Function IstFeiertag(Datum As Date) As String
  Dim Osterdatum As Date

  If Day(Datum) = 1 And Month(Datum) = 1 Then
    IstFeiertag = "Neujahr"
  ElseIf Day(Datum) = 1 And Month(Datum) = 5 Then
    IstFeiertag = "Maifeiertag"
  ElseIf Day(Datum) = 3 And Month(Datum) = 10 Then
    IstFeiertag = "Tag der Deutschen Einheit"
  ElseIf Day(Datum) = 25 And Month(Datum) = 12 Then
    IstFeiertag = "1. Weihnachtstag"
  ElseIf Day(Datum) = 26 And Month(Datum) = 12 Then
    IstFeiertag = "2. Weihnachtstag"
  Else
    Osterdatum = HolOsterdatum(Year(Datum))

    If Datum = Osterdatum - 2 Then
      IstFeiertag = "Karfreitag"
    ElseIf Datum = Osterdatum Then
      IstFeiertag = "Ostersonntag"
    ElseIf Datum = Osterdatum + 1 Then
      IstFeiertag = "Ostermontag"
    ElseIf Datum = Osterdatum + 39 Then
      IstFeiertag = "Christi Himmelfahrt"
    ElseIf Datum = Osterdatum + 49 Then
      IstFeiertag = "Pfingstsonntag"
    ElseIf Datum = Osterdatum + 50 Then
      IstFeiertag = "Pfingstmontag"
    End If
  End If
End Function

Private Function HolOsterdatum(Jahr As Integer) As Date
  Dim a As Integer, b As Integer, c As Integer
  Dim d As Integer, e As Integer
  Dim Tag As Integer, Monat As Integer

  a = Jahr Mod 19
  b = Jahr Mod 4
  c = Jahr Mod 7
  d = (19 * a + 24) Mod 30
  e = (2 * b + 4 * c + 6 * d + 5) Mod 7

  Tag = 22 + d + e
  Monat = 3

  If Tag > 31 Then
    Tag = d + e - 9
    Monat = 4
  ElseIf Tag = 26 And Monat = 4 Then
    Tag = 19
  ElseIf Tag = 25 And Monat = 4 And d = 28 And e = 6 And a > 10 Then
    Tag = 18
  End If

  HolOsterdatum = DateSerial(Jahr, Monat, Tag)
End Function