30分間は同じ値です。

time.py

# -*- coding: utf-8 -*-

import datetime
import time

fmt = '%Y-%m-%d %H:%M'
add = datetime.timedelta(minutes=1)
start = datetime.datetime(2016, 12, 30, 17, 0, 0)
while(1) :
    a = start.strftime(fmt)
    #print start.strftime('%s')
    #print (int)(start.strftime('%s'))
    b = (int)(start.strftime('%s')) // ( 60 * 30 )
    print a, ' ', b
    start = start + add
    time.sleep(1)