I am using a new iMac with Snow Leopard and the latest update of PhotoMechanic (ver 4.6.
When I go to "TOOLS" and "Adjust Capture Dates and Times" I can change the date, hour and minute but not the seconds! (which is pretty important).
My wife can do this on her laptop and desktop (one with Mac OS LION, the other with Mac OS LEOPARD).
Here is a screen shot from my Mac:
Here is what my wife's photomechnic shows in the same tool function: