In 1752 Parliament passed the Calendar Act. It was a nifty two-step change to convert the United Kingdom and her colonies to the Gregorian calendar once and for all.
Step 1: It was decreed that the year 1752 would end on December 31st instead of on the following March 25th, thereby lopping nearly three months off the year.
Step 2: A further eleven days were removed from the month of September to bring us into line with the Gregorian calendar. One day it was September 2nd, next day it was September 14th.
1752 was a very short year and as you may imagine, when the next Lady Day came round and rents and taxes were due people objected. They felt they were being robbed of time. Well in a sense they were. So the Exchequer said, ‘Okay, we’ll give you eleven days grace.’ And because there was an intervening Sunday, April 6th was fixed as the start of the new tax year. Which is where it has remained to this very day.
So now you know. Just call me Wrassles-with-Calendars