The dates presented are supposed to be the date when area was added in the game. However, this information can be inaccurate for various reasons; many of these dates originate from old newsposts made by wizards and the area may have actually been in the game for a while before the post was made. Some dates may be for recodes of the area. Some dates are from post-1996 conversion while the area may have existed before.

You may also be interested in the PupuMaps project changelog, which lists other kind of changes made to the data.