Geordie
“I suppose because when the original people settled there, they arrived by boat and possibly weren’t aware of the days or the different shitos in the rishonim. So they just kept Shabbos on Saturday like it is in most places of the settled world.”
Actually according to Rav tzvi PEsach Frank and Rav Isser Zalman MEltzer this is the halacha. They hold Shabbos is when that locale considers Saturday.