Use the datetime module.
>>> import datetime
>>> start = datetime.datetime.strptime(u'2013-05-20 05:09:06', '%Y-%m-%d %H:%M:%S')
>>> end = datetime.datetime.strptime(u'2013-05-20 05:10:06', '%Y-%m-%d %H:%M:%S')
>>> (end - start).total_seconds()
60.0