Для Python 2.5 +
from datetime import datetime
format = '%Y-%m-%d %H:%M:%S'
print datetime.strptime(time2, format) -
datetime.strptime(time1, format)
# 1 day, 0:00:00
Редактировать: для Python 2.4
import time
format = '%Y-%m-%d %H:%M:%S'
print time.mktime(time.strptime(time2, format)) -
time.mktime(time.strptime(time1, format))
# 86400.0