private void _mDateTimePicker_ValueChanged(object sender, EventArgs e)
{
_mManager.Start = _mStartDatePicker.Value;
var span = DateTime.Today - _mManager.Start;
_mManager.Now = (int)Math.Round(span.TotalDays);
if (_mManager.TimeScale == TimeScale.Week) _mManager.Now = (_mManager.Now % 7) * 7;
_mChart.Invalidate();
}