Monitoring is my bread an butter. I had cause to re-write a script here that parses process running time from ps output.

ps -ef "%t %c"
      29:23 swdmgr
 3-09:32:03 RIM_Oracle_prog
   07:13:13 ksh
[download]

That running time is days-hours:minutes:seconds. Where days and hours will only be there if non-zero. The existing code parsed it like this:

   my ($days, $hours, $min, $secs);
   if ($time=~/(\d+)-(\d{2}):(\d{2}):(\d{2})/){
      $days=$1;
      $hours=$2;
      $mins=$3;
      $secs=$4;
   }elsif($time=~/(\d{2}):(\d{2}):(\d{2})/){
      $hours=$1;
      $mins=$2;
      $secs=$3;
   }else{
      ($mins,$secs)=split/:/,$time;
   }
   my $day_sec=$days*86400;
   my $hour_sec=$hours*3600;
   my $min_sec=$mins*60;
   my $secs_running=$day_sec+$hour_sec+$min_sec+$secs;
[download]

But I thought this was much more fun...

    my $age; # age in seconds
    $age = $1 * 86400 if $time =~ s/(\d+)-//; # add days if there
    my ($hours,$min,$sec) = split /:/, $time;
    my @mult = (1, 60, 3600);
    for (reverse split /:/, $time) { # fun way to convert to seconds
        $age += $_ * shift @mult;    # he he he :-)
    }
[download]

Cheers,
R.