While I agree with this to an extent, MySQL also has a ton of functions for
modifying and comparing dates. The TIMESTAMP type tends to be useless for what
the OP is looking for -- as it gets updated each time the record is updated.
However, DATETIME does not, and it becomes fairly trivial to write SQL that can
do date/time comparisons on such fields. The reason I would prefer to use the
SQL over using perl in this instance is that it's portable; if I choose to
use another language, I can use the same SQL for doing the comparison.
I leave it up to the OP to look up the date and time functions; they're very
well documented on the MySQL site. (Which is where s/he should have started
looking, really... :-)