I also display 30 days in my axis and one solution I found was the following:
axis.Categories(s => s.UpgradeDate);
axis.Labels(l => l.Rotation(50));
That works great for Columns, however when I change it to Bars the dates move to the vertical line (which is the normal behaviour) and they are all crunched. I still have plenty of room in the screen, not sure why the space between the dates are not streched or why the height of the chart is not extended giving more space among the data grid lines.
If you could shed some light here I'd appreciate it.