how to compare file modification time (whole dir tree?)

[Leslie Mikesell]

>>newer file1 file2
>>that returns 0 if file1 is newer than file2 else returns 1

I would like something a little more ambitious.  Given two machines
(non-network) that have had files transfered with cpio -m (keep mod dates)
and some files changed on each machine, what is the best way to find
all the changed files?
Also, is there a handy way to set the timestamp on a directory to that
of the newest file below it?  This would help to avoid the problem above
and might be used in a first pass of the comparison.

Les Mikesell
  les at chinet.chi.il.us