Here's some notes from the history page of St. Mary Parish, Arnold in Nottingham:
"The church is dedicated to St. Mary, and the patronal festival to commemorate the Nativity of the Virgin is held in Amold on the Sunday following the 19th September and not the 8th September as noted in the "Church Calendar". If we go back to 1752 we would see that, because of past incorrect calculations with solar time which affected the reckoning connected with the calendar, eleven days had been lost. The 3rd of September 1752 was decreed by Parliament to become the 14th September, thereby correcting the calendar. The people of Arnold, however, still kept the same day : Nothing had happened! So, instead of celebrating the patronal festival on the Sunday following the 8th September, continued to use the old-established day, which made it the 19th September."
Apparently they keep their patronal feast day (Nativity of the Mother of God) on the Old Calendar! That's good enough reason for me switch!
Here's a link to the church's website. Click on history to read the whole story!