mDT = New DataTable
With mDT
    .Columns.Add("ID", GetType(Integer))
    .Columns(0).AutoIncrement = True
    .Columns(0).AllowDBNull = False
    .Columns(0).Unique = True
 
    .Columns.Add("Tag", GetType(String))
    .Columns.Add("Datum", GetType(Date))
    .Columns.Add("Start", GetType(Date))
    .Columns.Add("Ende", GetType(Date))
    .Columns.Add("Pause", GetType(Integer))
    .Columns.Add("Soll AZ", GetType(Integer))
    .Columns.Add("Bemerkung", GetType(String))
    .AcceptChanges()
End With

Private Sub btnAddNew_Click(ByVal sender As Object, ByVal e As _
  System.EventArgs) Handles btnAddNew.Click
 
    Dim DateFrom As Date = New Date(2019, 9, 16)
    Dim DateTo As Date = New Date(2019, 9, 22)
    Dim n As Integer = CInt((DateTo.Date - DateFrom.Date).TotalDays)
 
    For i As Integer = 0 To n
 
        Dim D As Date = DateFrom.Date.AddDays(i)
 
        Dim DR As DataRow = mDT.NewRow
        'DR.Item(0) = Nothing
        DR.Item(1) = D.ToString("ddd")
        DR.Item(2) = D
 
        If D.DayOfWeek = DayOfWeek.Saturday Or D.DayOfWeek = DayOfWeek.Sunday _
          Then
            DR.Item(3) = D
            DR.Item(4) = D
            DR.Item(5) = New TimeSpan(0, 0, 0).TotalMinutes
            DR.Item(6) = New TimeSpan(0, 0, 0).TotalMinutes
            DR.Item(7) = "WE"
        Else
            DR.Item(3) = D.Add(New TimeSpan(7, 30, 0))
            DR.Item(4) = D.Add(New TimeSpan(16, 0, 0))
            DR.Item(5) = New TimeSpan(0, 45, 0).TotalMinutes
            DR.Item(6) = New TimeSpan(6, 48, 0).TotalMinutes
            DR.Item(7) = "Anwesend "
        End If
 
        mDT.Rows.Add(DR)
    Next
 
End Sub