Something

Option Strict On
Imports System.Console
Module Module1
    Sub Main()
        Dim dag, jatko, strpvm As String
        jatko = "k"
        While jatko <> "e" And jatko = "k"
            Do
                Clear()
                Write("Anna päivämäärä: (d.m.Y) ")
                strpvm = CStr(ReadLine())
            Loop Until IsDate(strpvm)
            Select Case CDate(strpvm).DayOfWeek
                Case DayOfWeek.Sunday : dag = "Sunnuntai"
                Case DayOfWeek.Monday : dag = "Maanantai"
                Case DayOfWeek.Tuesday : dag = "Tiistai"
                Case DayOfWeek.Wednesday : dag = "Keskiviikko"
                Case DayOfWeek.Thursday : dag = "Torstai"
                Case DayOfWeek.Friday : dag = "Perjantai"
                Case DayOfWeek.Saturday : dag = "Lauantai"
            End Select
            WriteLine(dag)
            Do
                WriteLine("Jatketaanko? (k tai e)")
                jatko = CStr(ReadLine()).ToLower
            Loop Until jatko = "k" Or jatko = "e"
        End While
    End Sub
End Module