pydata/pandas — pull request #3491 by kevinastone (2013-04-30 08:35:55+00:00)
Title: Failing Unit Test and Patch for Fixing MonthEnd DateRange Unions with Timezones

This patch preserves the timezone information when applying an offset to `DatetimeIndex` with a timezone applied. The `MonthEnd` Offset wasn't retaining the timezone information resulting in an error even when both indexes had timezones.

```
TypeError: can't compare offset-naive and offset-aware datetimes
```