What system are you on?
What information do you want to find out?
If you are on an AS400, and you have the job name, you can search QHST to get the start and stop time. Use DSPLOG WHST
If you looking for the joblog, use DSPJOB. The joblog may no longer exists if if completed normally. If there was printed output and it has been printed and not setup as *SAV, it will also be gone.
If you do journaling, you could look at the journals to find what thingk changed.