cron log file location

[ken_yap]

!????? How do you mean? Every line in /var/log/messages has a timestamp when the event happened so you know when the job was started.

[beli0135]

This one doesnt...

I set event in 8:40, I have messages till 8:38 and returning back at 8:42
and process executed as I typed "ps -A" in 8:40 and it was running.

[ken_yap]

I don't understand your sentences.

Only the start time of the job (by the computer clock of course) and the command are logged. It doesn't log how long the command took, or when it finished.

If you need to know these things, you can put your own commands in the cron job before and after the work. E.g.

10 2 * * * /bin/date; /usr/local/bin/somecommand; /bin/date

The output of the job is mailed to the owner of the job, root if a system job. If you want to capture the output, you can use shell redirection. E.g.

10 2 * * * (/bin/date; /usr/local/bin/somecommand; /bin/date) > /root/job.log 2>&1