B4R Code Snippet Day of week calculation

Private Sub weekday(day As Int, month As Int, year As Int) As Int


    Dim dayofweek As Int ' day of week
    month = month -2
    If month = -1 Then
        month = 11
    End If
    If month = 0 Then
        month = 12
    End If
    Dim c As Int = Floor(year/100)
    Dim d As Int = year - c*100

    Dim f As Int = day + (Floor(13*month-1)/5) +d+ Floor(d/4) +Floor(d/4)-2*c
    dayofweek = f Mod 7
    If dayofweek < 0 Then dayofweek=dayofweek + 7 'Sunday = 0
    Return dayofweek
End Sub