This is the difference between Python 2 and 3, yes.
Python 2.7.3 (default, Apr 10 2012, 23:31:26) [MSC v.1500 32 bit (Intel)] on win32
Type "help", "copyright", "credits" or "license" for more information.
>>> from datetime import datetime
>>> now = datetime.now()
>>>
>>> print ('%s/%s/%s') % (now.year, now.month, now.day)
2014/2/23
Python 3.3.2 (v3.3.2:d047928ae3f6, May 16 2013, 00:03:43) [MSC v.1600 32 bit (Intel)] on win32
Type "help", "copyright", "credits" or "license" for more information.
>>> from datetime import datetime
>>> now = datetime.now()
>>>
>>> print ('%s/%s/%s') % (now.year, now.month, now.day)
%s/%s/%s
Traceback (most recent call last):
File "<stdin>", line 1, in <module>
TypeError: unsupported operand type(s) for %: 'NoneType' and 'tuple'
>>> print ('{0}/{1}/{2}'.format(now.year, now.month, now.day))
2014/2/23
The core of it centers around the difference between print
being a statement in Python 2 and a function in Python 3.