In Philadelphia we have something called “Philadelphia datum,” where a foot is not equal to 12.0”, but some near portion of that. Something to do with a historical innacurracy from when the city was first laid out and surveyed centuries ago. Since it was memorialized in all the original deeds, and perpetuated ever since, it has persisted. But as I understand it, metes and bounds cited in deeds need to be converted to actual measurements you use in site. Occasionally it causes significant problems when someone doesn’t know, or forgets.