You need to import module datetime and then use function strptime() from that module. Here is an example:
>>> t1='2003-01-01'>>> from datetime import datetime>>> t2=datetime.strptime(t1, '%Y-%m-%d')>>> t2datetime.datetime(2003, 1, 1, 0, 0)>>> t2.year2003>>> t2.month1>>> t2.day1>>> t1='2003-12-31'>>> t3=datetime.strptime(t1, '%Y-%m-%d')>>> t3datetime.datetime(2003, 12, 31, 0, 0)>>> t2datetime.datetime(2003, 1, 1, 0, 0)>>> t3-t2datetime.timedelta(364)>>> (t3-t2).days364