Get the difference between two datetime objects in minutes in python

Question

I have two datetime objects created by strptime in Python:

date_string = "Wed, 18 Dec 2013 09:30:00 GMT"
date = datetime.datetime.strptime(date_string, "%a, %d %b %Y %H:%M:%S %Z")

and

end_date_string = "Wed, 18 Dec 2013 10:15:00 GMT"
end_date = datetime.datetime.strptime(end_date_string, "%a, %d %b %Y %H:%M:%S %Z")

Datetime objects are created successfully so i get

>>>date
datetime.datetime(2013, 12, 18, 9, 30)
>>>end_date
datetime.datetime(2013, 12, 18, 10, 15)

I want to count the minutes the two datetimes differ. I do

diff = end_date - date

and i get

 datetime.timedelta(0)

So it says that they are the same dates?No difference at all? Also seconds property is zero

>>>diff.seconds
0

How can this be made to work?