Here I have rejigged your code somewhat to compile under strict and warnings, however I have tried to leave it as original as possible so you find it familiar and easy to understand.

#!/usr/bin/perl 
use warnings;
use strict;
use Time::Local; 

my $x = getTime();
my $d1;
my $d2; 
my $ID; 
my $epoch;
my %openTime;
my %account;
my %totalSession;
my %dSession;

sub getTime
{
     (my $sec,my $min,my $hour,my $mday,my $month,my $year,my $wday,my
+ $yday,my $isdst)=localtime(time);
 $epoch = timelocal($sec, $min, $hour, $mday, $month, $year);
 return $epoch;
}
my @fileTotal = `ls /u/user/myarea/test/file*`;
#foreach loop opens each log file
foreach my $file (@fileTotal)
{ 
     chomp($file);
     open(FILEREAD, "< $file");
     open FILEREAD, "< $file" or die "Can't open $file for reading - $
+?";
     while (my $linebuf = <FILEREAD>)
     { 
          chomp($linebuf);          # remove <CR> at the end
          my @data = split(/[ ]+/, $linebuf);
          if( $data[6] eq "session" && $data[7] eq "opened")
          { 
               $d1 = index($linebuf, "[", 0);
               $d2 = index($linebuf, "]", ($d1+1));
               $ID = substr($linebuf, ($d1+1), ($d2-$d1-1));
               $openTime{$ID} = $epoch;
               $account{$ID} = $data[10];
               print "open time= $openTime{$ID}\n";
          }
          elsif( $data[6] eq "session" && $data[7] eq "closed")
          {
               # user SSH logoff session
               $d1 = index($linebuf, "[", 0);
               $d2 = index($linebuf, "]", ($d1+1));
               $ID = substr($linebuf, ($d1+1), ($d2-$d1-1));
               my $closeTime = $epoch;
               print "closetime= $closeTime\n";
               if( defined $account{$ID})
               {
                    my $userAccount = $account{$ID};
                    my $duration = $closeTime - $openTime{$ID}; #inter
+val
                    $totalSession{$userAccount}++;
                    $dSession{$userAccount} += $duration;
               }
          }
     }
     close FILEREAD;
}

foreach $x (sort(keys %totalSession))
{ 
     my $averageSession = $dSession{$x}/$totalSession{$x};
     printf "%-10s %10s %10s \t %.2f\n",$x,$totalSession{$x},$dSession
+{$x},  $averageSession;
}
[download]

I used this as an example fo input:

 Jan 31 08:40:19 ubuntu01 sshd[32346]: pam_unix(sshd:session): session opened for user user1 by (uid=1)

 Jan 31 08:45:19 ubuntu01 sshd[32346]: pam_unix(sshd:session): session closed for user user1 by (uid=1)

That I found in what I believe to be an alternate post of yours.

As you will be able to see from a simple output debug I put in, epoch is printed on both 'opened' and 'closed' and prints the same number, hence you're '0's issue. I would suggest rethinking your method of determing 'time' and the difference between a 'connection open' time and a 'connection closed' time.

By no means am I guaranteeing that this code is the best way to do it, it is simply my honest interpretation from your's to 'safe/compilable code' - My usual caveat applies - all edits and suggestions and errors found are more than welcomed as always.

All the best - your ever faithfull functioning perloHolic