Подсчет времени

def count_days_issuing(id_auto):
    register_type(UNICODE)
    conn = psycopg2.connect(CONN_STR)
    cur = conn.cursor()
    cur.execute('select date_issue from issuing_auto where id_auto=(%s)', [id_auto])
    cols = cur.description
    row = cur.fetchone()
    summ=0
    cur2 = conn.cursor()
    cur2.execute('select return_date from issuing_auto where id_auto=(%s)', [id_auto])
    cols = cur2.description
    row2 = cur2.fetchone()
 
    while row:
        for i in xrange(len(cols)):
             d= str(row[i])
             dv= str(row2[i])
             year,month,day=d.split('-')
             t2=date(int(year),int(month),int(day))
             print t2
             year,month,day=dv.split('-')
             t3=date(int(year),int(month),int(day))
             print t3
             time=t3-t2
             print time
             summ+=time
             print '#'*10
        row = cur.fetchone()
        row2 =cur2.fetchone()
    cur.close()
    conn.close()

>>> import datetime
>>>
>>> t1 = datetime.date(2015,12,22)
>>> t2 = datetime.date(2016,1,1)
>>>
>>> t3 = datetime.date(2016,1,1)
>>> t4 = datetime.date(2016,12,31)
>>>
>>> td1 = t2-t1
>>> td2 = t4-t3
>>>
>>> summ = datetime.timedelta(0)
>>>
>>> summ += td1
>>> summ
datetime.timedelta(10)
>>>
>>> summ += td2
>>> summ
datetime.timedelta(375)
>>>

from datetime import timedelta