Issue1950

datetime.date.__add__() should return NotImplemented instead of raising TypeError, as is already mentioned in source code.
This change fixes errors in test suite of python-dateutil (http://pypi.python.org/pypi/python-dateutil).
--- Lib/datetime.py
+++ Lib/datetime.py
@@ -911,8 +911,7 @@
 self._checkOverflow(t.year)
 result = date(t.year, t.month, t.day)
 return result
- raise TypeError
- # XXX Should be 'return NotImplemented', but there's a bug in 2.2...
+ return NotImplemented
 
 __radd__ = __add__

But, this is the behavior of CPython 2.7 (I think it is fixed in 3.3)
Python 2.7.3 (default, Apr 20 2012, 22:39:59) 
[GCC 4.6.3] on linux2
Type "help", "copyright", "credits" or "license" for more information.
>>> from datetime import date
>>> x = date(1,2,3)
>>> y = date(4,5,6)
>>> x + y
Traceback (most recent call last):
 File "<stdin>", line 1, in <module>
TypeError: unsupported operand type(s) for +: 'datetime.date' and 'datetime.date'

Marking this as deferred in hopes that we remember to fix this in 3.3.

The suggested change in Lib/datetime.py is still correct, but apparently Jython incorrectly handles NotImplemented (issue #1955).

Is dateutil using the datetime internals in some way?
Re support in 3.x, let's not use bugs here to remind us of that sort of functionality, hopefully it's in a unit test.

python-dateutil defines class dateutil.relativedelta.relativedelta with __add__() method, which allows addition operation between instances of datetime.date and dateutil.relativedelta.relativedelta.
$ python2.7 -c 'import datetime, dateutil.relativedelta; print(datetime.date(2014, 5, 22) + dateutil.relativedelta.relativedelta(months=3))'
2014年08月22日
$ jython2.7 -c 'import datetime, dateutil.relativedelta; print(datetime.date(2014, 5, 22) + dateutil.relativedelta.relativedelta(months=3))'
Traceback (most recent call last):
 File "<string>", line 1, in <module>
 File "/usr/share/jython-2.7/Lib/datetime.py", line 925, in __add__
 raise TypeError
TypeError

Except for three exceptions re "This test fails if you don't have the dateutil timezone file installed", all dateutil tests now pass against https://github.com/dateutil/dateutil/
Duplicate of #2010. #1995 is not relevant since this update of datetime uses new style classes
Fixed by https://hg.python.org/jython/rev/daa6bf9a14d5 

Or rather, *no longer* relevant