There could be many reasons why the town and you disagree on the date of your home. A fire, flood, or other event may have destroyed town records and property dates changed because of the lack of info. The town may not have begun recording dates of construction until that time. Just because a map shows a structure on your site does not mean it is the current structure as you know it.
You need to have a concrete idea as to why you wish to change the recorded date and determine what benefit it brings to you to change it. Most commonly, earlier recorded dates of structures are desired to make them eligible for grants and public funds to restore the structure to its original style/function. Doing this will also restrict what changes may be made in the future, possibly making the property less valuable to others. If the earlier date is indeed correct, you can probably pursue the change at any time in the future (ask at the town hall to confirm this), but once the change is made it is unlikely that you will be able to change it back. Your hands would be tied at that point. Right now, it's all just potential, and that potential can probably be passed on to the next buyer without costing you a decrease in value due to restrictions placed on it.
good luck- Paul