You could use python-dateutil.
In [4]: from datetime import datetime
In [5]: date1 = datetime.strptime(str('2011-08-15 12:00:00'), '%Y-%m-%d %H:%M:%S')
In [6]: date2 = datetime.strptime(str('2012-02-15'), '%Y-%m-%d')
In [7]: from dateutil import relativedelta
In [8]: r = relativedelta.relativedelta(date1, date2)
In [9]: r
Out[9]: relativedelta(months=-5, days=-30, hours=-12)