Python: Look What the Stork Dragged In

I have this Python program that I haven't run in a couple years. I wanted to see if I could make it run faster. Last time, it took 22 hours. Sure enough, using some advanced optimization techniques (and a swig of castor oil), my wife and I were able to run the program in a mere 6.5 hours! Here it is:

#!/usr/bin/env python

"""Help Gina-Marie time her contractions."""

import time

SECS_PER_MIN = 60


last_start = None
while True:
    print "Press enter when the contraction starts.",
    raw_input()
    start = time.time()
    if last_start:
        print "It's been %s minutes %s seconds since last contraction." \
            % divmod(int(start - last_start), SECS_PER_MIN)
    last_start = start
    print "Press enter when the contraction stops.",
    raw_input()
    stop = time.time()
    print "Contraction lasted %s seconds." % int(stop - start)
    print