import datetime
import time
#string to datetime
str = '2015-11-19'
date_time = datetime.datetime.strptime(str,'%Y-%m-%d')
#datetime to string
str = date_time.strftime('%Y-%m-%d')
import datetime
import time
#string to datetime
str = '2015-11-19'
date_time = datetime.datetime.strptime(str,'%Y-%m-%d')
#datetime to string
str = date_time.strftime('%Y-%m-%d')