Bad x-axis dates when plotting two time-series with different indexes (start, end, and freq)
The two DataFrames are from 2014, but from the figure you can see that pandas throws one of them to the year 2050!

![bad_pandas](https://cloud.githubusercontent.com/assets/950575/6272178/7ec299a6-b844-11e4-81a7-c47c1a3293bf.png)

I am using pandas 0.15.2 and the notebook below describes the problem and show a few workarounds that might help debug this:

http://nbviewer.ipython.org/gist/ocefpaf/e7e085c84fd3ea7dbc24

Here is a quick SSCCE to generate the figure above:

``` python
import numpy as np                                                                               
import pandas as pd                                                                              

index = pd.date_range(start='2014-06-01 00:00:00', end='2014-09-01 00:00:00', freq='H')          
data = np.random.rand(len(index))                                                                
df0 = pd.DataFrame(data=data, index=index, columns=['DF0'])                                      
index = pd.date_range(start='2014-04-07 10:57:00', end='2014-10-29 09:32:00', freq='D')          
data = np.random.rand(len(index))                                                                
df1 = pd.DataFrame(data=data, index=index, columns=['DF1'])                                      

ax = df0.plot(legend=True, figsize=(12, 4))                                                      
ax = df1.plot(ax=ax)                                                                             
```

Thanks!
