Cairo + plot_date = misaligned x-axis labels

On OSX 10.8.2, using the cairo backend along with plot_date leads to misaligned x-axis labels. No combination I found of setting the verticalalignment of the label (top, bottom, baseline, etc), solved this problem. 

Here's a screenshot of the issue (Notice the vertical alignment of April & May).

![bug](https://f.cloud.github.com/assets/150536/226195/8789a618-8620-11e2-89c4-7075f6038481.png)

Here's a gist with minimal code to reproduce the issue. It contains all the info about my matplotlib version, setup, etc. that should be needed.

https://gist.github.com/jsundram/5096973