since 2015-02-13

https://labix.org/python-dateutil

$ sudo pip install python-dateutil==1.5
Password:
Requirement already satisfied (use --upgrade to upgrade): python-dateutil==1.5 in /System/Library/Frameworks/Python.framework/Versions/2.7/Extras/lib/python

$ python
Python 2.7.9 (default, Dec 14 2014, 10:02:06) 
[GCC 4.2.1 Compatible Apple LLVM 6.0 (clang-600.0.56)] on darwin
Type "help", "copyright", "credits" or "license" for more information.

>>> from dateutil.parser import *
>>> from dateutil.tz import *
>>> from datetime import *
>>> parse("2015-02-12T12:34:56.999Z")
datetime.datetime(2015, 2, 12, 12, 34, 56, 999000, tzinfo=tzutc())