Here are some resources I found on the key differences of the Gregorian Calendar and the Julian calendar. It might feel a bit repetitive having this expert from the Nottingham article and the YouTube video. However, the information is important to know and I know it can be confusing at times. Please check out the Calendar that has published under our resources tab. Click around on the different days to learn more!
The article from Nottingham was very informative but here is the few sentences that I thought would be the most helpful for us as we learn the difference between the Gregorian and the Julian calendars.
“The Julian Calendar was the system of dating followed from 46BC onwards. It was this calendar which added one extra day in every four years (giving us our ‘leap year’) because it had been calculated that the earth takes 365¼ days to complete its circuit around the sun, not a straight 365 days.
Unfortunately, this calculation was not entirely accurate. In fact, the sun’s circuit is not exactly 365¼ days – it’s approximately 11 minutes less. This may seem a very small amount, but over a large number of years the figure builds up. As a result, it emerged that the Julian Calendar was over-correcting by around 8 days each millennium.
In the 16th century the problem was examined. A solution was hit upon whereby centenary years would not be leap years unless they were divisible by 400. This meant that three out of four centenary years would not be leap years, or, that in every 400 years there would not be 100 leap years but 97. Using this calculation meant that there would only be an over-correction of 23 seconds, and that it would take 3,700 years before the over-correction amounted to a full day.
In 1582 Pope Gregory ruled that this new calendar – thereafter called the Gregorian Calendar – should be brought into use. By that stage, the Julian Calendar had added ten days too many to the calendar, so Pope Gregory decreed that the day after the 4th of October 1582 should be the 15th of October 1582, thus correcting the error.”
https://www.nottingham.ac.uk/manuscriptsandspecialcollections/researchguidance/datingdocuments/juliangregorian.aspx
