Trivia fact of the day: On September 2, 1752, Britain converted from the Julian to the Gregorian calendar. Which conversion necessitated losing 11 days, as they skipped ahead to catch up. You will not find any 250-year anniversaries in British history between now and Sept 14, because those days didn't exist 250 years ago.
Here's a fascinating, if brief, article about the conversion, including riots with the rallying cry "Give us back our eleven days," from simple folk who thought 11 days had somehow been stolen from their lives. Which reminds me of a quote (which I unfortuantely cannot cite) from an Alabama farmer opposed to daylight savings time, on the grounds that the extra hour of sunlight would hurt his tomatoes.