Time Difference

[GMane Python]

Hello
  I was wondering if there is an existing function that would let me
determine the difference in time.  To explain:

Upon starting a program:

startup = time.time()

After some very long processing:
now = time.time()

print <days> <hours> <minutes> <seconds>, now - startup

So, to print in a formatted way (D-H-M-S) the difference in time of startup
and now.

Thanks!
Dave