BUG: PandasAutoDateLocator num_days calculation is wrong
This line in PandasAutoDateLocator looks like it's missing some parentheses.

https://github.com/pandas-dev/pandas/blob/master/pandas/tseries/converter.py#L264
        num_days = ((delta.years * 12.0) + delta.months * 31.0) + delta.days

I stepped through here and with a delta of 5 years, num_days was 60! It's easy enough to fix:

        num_days = (((delta.years * 12.0) + delta.months) * 31.0) + delta.days