Make sysadmin dashboard gitlog date timezone-aware

@carsongee Just a small change to the sysadmin dashboard gitlog:
* Redundancy reduced in the template
* Date is timezone aware and formatted as `util.date_utils.DEFAULT_DATE_TIME_FORMAT`

Before:
-----------
![before](http://i.imgur.com/71heogf.png)

After:
--------
![after](http://i.imgur.com/GnBQvzQ.png)


Please put a space between the `%` and `for`, as it was before.