Preventing date rollback

[Richard "Tiger" Melville]

Many of the software products our company sells rely on a licence file which
specifies the duration of time the software is licensed for.  The software
then refuses to run when the period has expired.  It is, however, possible
to roll back the date on a machine and fool the licence manager software.
This problem must be solved in order for us to distribute free demo versions
which work for a specified period only.

Is there a reliable way to test if the date on a machine has been rolled
back ?  (System files which have modified dates in the future might do the
trick.)  As portable a solution as possible is desirable, although we mainly
run SunOs 4.0.

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             _Q     Q_       Richard Melville DataSpan Technology Inc.  
      __    /_\)   /|        237-9313         400-540 5th ave SW
_\___/O____O|/O____/ \_                       Calgary Alberta Canada, T2P 0M2
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