Five weekends

'https://rosettacode.org/wiki/Five_weekends
Imports System
Module Program
    Sub Main()

        Dim aMonth As Short() = {1, 3, 5, 7, 8, 10, 12}              'All 31 day months
        Dim aMMStore As New List(Of String)                          'To store results
        Dim siYear, siMonth, siCount As Short                        'Various variables
        Dim dDay As Date                                             'To store the day to check
        Dim sTemp As String                                          'Temp string

        For siYear = 1900 To 2100                                    'Loop through each year
            For siMonth = 0 To 6                                     'Loop through each 31 day month
                dDay = New Date(siYear, aMonth(siMonth), 1)          'Get the date of the 1st of the month
                If Weekday(dDay) = 6 Then
                    aMMStore.Add(Format(dDay, "MMMM yyyy"))          'If the 1st is a Friday then store the result
                End If
            Next
        Next

        For Each sTemp In aMMStore 'For each item in the stored array..
            siCount += 1 'Increase siCount
            If siCount < 6 Then Console.WriteLine(aMMStore(siCount))                        'If 1 of the 1st 5 dates then print it
            If siCount = 6 Then Console.WriteLine(New String("-", 14))                      'Print a separator
            If siCount > aMMStore.Count - 5 Then Console.WriteLine(aMMStore(siCount - 1))   'If 1 of the last 5 dates then print it
        Next

        Console.WriteLine("Total months = " & Str(siCount))          'Print the number of months found

        siCount = 0                                                  'Reset siCount
        sTemp = String.Join(",", aMMStore)                           'Put all the stored dates in one string joined by commas
        aMMStore.Clear() 'Clear the store for reuse

        For siYear = 1900 To 2100                                    'Loop through each year
            If InStr(sTemp, Str(siYear)) = 0 Then                    'If the year is not in the stored string then..
                siCount += 1                                         'Increase siCount (Amount of years that don't have 5 weekend months)
                aMMStore.Add(Str(siYear))                            'Add to the store
            End If
        Next

        Console.WriteLine()
        Console.WriteLine("There are " & Str(siCount) &
                          " years that do not have at least one five-weekend month")    'Print the amount of years with no 5 weekend months
        Console.WriteLine(String.Join(",", aMMStore))                                   'Print t

    End Sub
End Module