JOUR FERIÉ EN VB.NET

    Function BooJourFerie(ByVal Jour As Date) As Boolean
        Dim JJ, AA, MM As Integer
        Dim NbOr, Epacte As Integer
        Dim PLune, Paques, Ascension, Pentecote As Date

        JJ = Microsoft.VisualBasic.Day(Jour)
        MM = Month(Jour)
        AA = Year(Jour)

        If JJ = 1 And MM = 1 Then BooJourFerie = True : Exit Function '1 Janvier
        If JJ = 1 And MM = 5 Then BooJourFerie = True : Exit Function '1 Mai
        If JJ = 8 And MM = 5 Then BooJourFerie = True : Exit Function '8 Mai
        If JJ = 14 And MM = 7 Then BooJourFerie = True : Exit Function '14 Juillet
        If JJ = 15 And MM = 8 Then BooJourFerie = True : Exit Function '15 Août
        If JJ = 1 And MM = 11 Then BooJourFerie = True : Exit Function '1 Novembre
        If JJ = 11 And MM = 11 Then BooJourFerie = True : Exit Function '11 Novembre
        If JJ = 25 And MM = 12 Then BooJourFerie = True : Exit Function '25 Décembre

        NbOr = (AA Mod 19) + 1
        Epacte = CType((11 * NbOr - (3 + Int((2 + Int(AA / 100)) * 3 / 7))) Mod 30, Integer)
        PLune = CDate("19/04/" & AA)
        PLune = PLune.AddDays(-((Epacte + 6) Mod 30))
        If Epacte = 24 Then PLune = PLune.AddDays(-1)
        If Epacte = 25 And (AA >= 1900 And AA < 2000) Then PLune = PLune.AddDays(-1)

        Paques = PLune.AddDays(-Weekday(PLune) + vbMonday + 7)   'Paques
        If JJ = Microsoft.VisualBasic.Day(Paques) And MM = Month(Paques) Then BooJourFerie = True : Exit Function

        Ascension = Paques.AddDays(38)   'Ascension
        If JJ = Microsoft.VisualBasic.Day(Ascension) And MM = Month(Ascension) Then BooJourFerie = True : Exit Function

        Pentecote = Ascension.AddDays(11)  'Pentecote
        If JJ = Microsoft.VisualBasic.Day(Pentecote) And MM = Month(Pentecote) Then BooJourFerie = True : Exit Function

        BooJourFerie = False
    End Function