You should start by reading the output of "perldoc -f time": 
  time    Returns the number of non-leap seconds since what­
          ever time the system considers to be the epoch
          (that's 00:00:00, January 1, 1904 for Mac OS, and
          00:00:00 UTC, January 1, 1970 for most other sys­
          tems).  Suitable for feeding to "gmtime" and
          "localtime".

          For measuring time in better granularity than one
          second, you may use either the Time::HiRes module
          from CPAN, or if you have gettimeofday(2), you may
          be able to use the "syscall" interface of Perl,
          see perlfaq8 for details.

[download]
So, based on this info, you probably want to kill a session when the difference between its start time and the current time is greater than (2*60*60), which is the number of seconds in two hours.

In reply to Re: Timestamps by graff
in thread Comparing timestamps by Anonymous Monk

Title:
Use:  <p> text here (a paragraph) </p>
and:  <code> code here </code>
to format your post, it's "PerlMonks-approved HTML":


  • Posts are HTML formatted. Put <p> </p> tags around your paragraphs. Put <code> </code> tags around your code and data!
  • Titles consisting of a single word are discouraged, and in most cases are disallowed outright.
  • Read Where should I post X? if you're not absolutely sure you're posting in the right place.
  • Please read these before you post! —
  • Posts may use any of the Perl Monks Approved HTML tags:
    a, abbr, b, big, blockquote, br, caption, center, col, colgroup, dd, del, details, div, dl, dt, em, font, h1, h2, h3, h4, h5, h6, hr, i, ins, li, ol, p, pre, readmore, small, span, spoiler, strike, strong, sub, summary, sup, table, tbody, td, tfoot, th, thead, tr, tt, u, ul, wbr
  • You may need to use entities for some characters, as follows. (Exception: Within code tags, you can put the characters literally.)
            For:     Use:
    & &amp;
    < &lt;
    > &gt;
    [ &#91;
    ] &#93;
  • Link using PerlMonks shortcuts! What shortcuts can I use for linking?
  • See Writeup Formatting Tips and other pages linked from there for more info.