private void changeStartPoint_Tapped(object sender, TappedRoutedEventArgs e)
{
if ((startPositions.Count % 2 == 0) && (startPositions.Count != 0))
{
//pivotDays.SelectedIndex = (pivotDays.SelectedIndex + startPositions.Count / 2) % startPositions.Count;
pivotDays.SelectedItem = pivotDays.Items[(pivotDays.SelectedIndex + startPositions.Count / 2) % startPositions.Count];
}
}
}