Adam,
That would depend on how you use your Mac. If you do nothing at all, your Mac will have the wrong time for three weeks in March and for one week in late October/early November.
For example, if you authenticate to a network, you may be prevented from doing so if your time is an hour off from the server attempting to authenticate you. And if you use a calendar program to keep track of appointments, you may not be on time for them, as the alarms may go off at the wrong time.
If you don't want to install any 'unofficial' patches to Panther, then why not just set your time zone one hour to the east on March 11, and then set it back to your normal time zone on April 1?
Then in the fall if you're still running Panther, you could set your time zone one hour to the east again on October 28, and back to normal on November 4.
Very quick and simple to do, and should have no repercussions.