Strange clock time, time warping???

[For Mongo]

One of my users has a process (nohup) that has been running since Monday
morning.  For accounting purposes (UTek doesn't have a builtin one, and the one
they sold us doesn't do backgroup processes if the parent dies), I created a
shell script to every five minutes do a ps -aeu and make sure it is still
running (is there any better way to do this?), however, looking at the log file
it creates, I noticed that the time was really screwed up.  If it is supposed
to be in minutes, it has somewhere gained almost a day.  I have noticed that
when comparing it to the real time, sometimes is has incremented by 10, and
sometimes five.  Can someone explain to me what exactly the time as give by a
ps command really is?

Steve