private void _mNowDatePicker_ValueChanged(object sender, EventArgs e)
{
TimeSpan span = _mNowDatePicker.Value - _mStartDatePicker.Value;
_mManager.Now = span.Days + 1;
if (_mManager.TimeScale == TimeScale.Week) _mManager.Now = _mManager.Now / 7 + (_mManager.Now % 7 > 0 ? 1 : 0);
_mChart.Invalidate();
}