Can't rotate text in graph
 

I have a pivot graph that has 2 levels on the x axis. One is date and one is
subject.

I'm trying to rotate the text so that it displays the text properly as it's
a big graph, but it only rotates one set of the data. The date is left
horizontal, out of line and is illegible. I've tried making the graph bigger
but it makes no difference.

Any ideas?

Thanks in advance:)