Matching the calendar to the solar year so that all the days align properly is a difficult thing since the solar year is 365 days, 5 hours, 48 minutes and a handful of seconds long. You can't chop that up evenly into days even if you had a clock accurate enough to give you that information.
The Julian (for Julius Caesar) Calendar made January 1 the beginning of the year and brought the system in line with the solar year. A gradual creep over the centuries put the calendar year 11 days off the solar year. The Gregorian (for Pope Gregory XIII) Calendar was closer to the natural cycle of the solar year. The Gregorian year was still about 26 seconds longer than a solar year.
Most of Europe switched to the Gregorian calendar in the 1500s, but Great Britain and other protestant countries saw no reason to follow a Pope’s decree.
For an agricultural based society this shift didn’t much change daily life but it did cause some confusion. George Washington was born on both February 11, and February 22. That’s just one example of how the loss of eleven days can mess things up. Another: imagine leaving London on June 28 and arriving in Paris on June 17th.
I hadn't yet figured out how all this would work for my characters when I set it aside to work on another project. In the time the three ring binder sat on the shelf, my subconscious dealt with the problem. When I picked up the work again last week and printed out a calendar for 1752, it was very clear the days were missing. September was three weeks long.
Some problems for my characters? You bet.
A major event, like the anniversary of the death of a child, was swallowed up along with the missing days. What is the poor mother to do when it is her habit to spend the day in seclusion? What will she do next year when the date is restored to the calendar, but in her heart is not the date of his death?
Poor Silas probably doesn't know when he has to get his paperwork to his boss the county sheriff. Rents are due, but the renter has fewer days to make the money to pay them.
And for this town in particular, a local festival has to be shifted to a date other than the traditional one. That would cut 11 days out of preparation time. Maybe it won't be as much fun this year. Maybe this isn't really much of a problem since the town is dealing with the murder of a stranger.