Things You Probably Didn't Know About the Gregorian Calendar

Things You Probably Didn't Know About the Gregorian Calendar
It was a miscalculation of 11 minutes in the Julian calendar and the postponement of Easter attributed to this error, that resulted in what we today know as the Gregorian calendar, or the civil calendar that is accepted worldwide. Here is an up-to-date account of this calendric reform.
Leap Year
Also, intercalary or bissextile year, it adds one extra day to keep the Gregorian calendar in sync with the astronomical or seasonal year. The next leap year, 2020, will thus have a 29th February.
What date is it today, while you read this? How many days passed since this article was written? How would you calculate this? Quite easy, if you got a calendar and add up the dates. Providing an organized chart of day, date, month, and year, a calendar makes it effortless to determine how time changes around us.

The Gregorian calendar is the most widely accepted system of dating and keeping track of time factor in the world. You must have heard about how countries fall under different time zones, which generates a time lag between them. Business activities run accordingly too. But imagine you are told to suddenly skip a week or two from the current month, and behave as if those few days never existed. That is what happened when the Gregorian calendar took over the former Julian calendar.
Interesting Facts About the Gregorian Calendar
The introduction of the Gregorian calendar brought about a drastic change in how the dates and days in a month were followed. Here are some fascinating facts about this transformation, that began in Western Europe.
Pope Gregory XIII
Also known as the Western calendar or Christian calendar, it was introduced in the year 1582 by Pope Gregory XIII, after whom it is named.
The Gregorian calendar was introduced by a papal bull (a charter by the Pope) issued on February 24, 1582.
The former system of the Julian calendar was said to be refined by the Gregorian calendar, when it corrected the length of a year by 0.002%.
The Gregorian calendar is a solar calendar, consisting of 365 days. It excludes three leap days every 400 years; whereas, in the Julian calendar, a leap year occurs every four years.
Easter Celebrations
This reform was brought in to adjust the date of Easter. The Julian calendar had miscalculated a year's length by 11 minutes. Easter (celebrated around March 21), which would normally fall around the spring equinox, was to be postponed further every year due to this error.
The papal bull could be enacted only for the Catholic Church and in the Papal sates, but not in other countries, as it had no authority to change the civil calendar. So, other nations had to adopt this new system for it to be enacted.
The Catholic countries of Europe were the first to adopt this reform. However, Protestants and other Eastern countries continued with the Julian calendar so that international trade was convenient. The celebrations of Easter by churches, therefore, still differed.
The Protestants had thought of this reform to be a plot by the Catholic Church to reverse and quieten the Protestant Reformation.
Spain, Portugal, most parts of Italy, the Polish-Lithuanian Commonwealth, and the Papal states in Italy witnessed this drastic skip of 10 days when they accepted the Julian 4th October, a Thursday to be followed by the Gregorian 15th October, a Friday in the year 1582.
Britain (including present-day eastern U.S., then a part of the British empire) adopted it in 1752, followed by Sweden in 1753. Some other nations to subsequently adopt it include: Japan (1872), China (1912), Russia and the Soviet Union (1918). Greece was the last country to begin following the new calendar in 1923.
The Gregorian calendar still uses the earlier calendar era, or year-numbering system, which is better known as the 'Common Era'. This Dionysian era begins the numbering of dates from 'Anno Domini', as first calculated by Dionysius Exiguus in the 6th century.
Aloysius Lilius, a doctor from southern Italy, had proposed a certain change in the Julian calendar. The actual reform was a modified version of this proposal.
The alteration was in two different parts: first, the reform of the Julian calendar; and second, the reform of the lunar cycle (accorded to by the Church to determine Easter dates).
He had also derived a practical method to adjust the 'epacts' of moon. Epact refers to the number of added days, on January 1, which are accounted for in the tabular methods while determining the date of Easter. This difference (usually of about 11 days) occurs due to the difference in the solar years (365 - 366 days), and lunar years (354 - 355 days). This used to be a major hurdle in calendar reform.
The difference between the year calculated in the Gregorian calendar and a solar year is around 26 seconds/year.
A reduction by 10 minutes and 48 seconds per year was also effected, as required by the change in the mean length of a year, i.e., from 365.25 days (365 days and 6 hours) to 365.2425 days (365 days, 5 hours, 49 minutes, 12 seconds).
Countries That Don't Use the Gregorian Calendar
There are still some countries that have not adopted the Gregorian calendar, including Saudi Arabia, Ethiopia, Nepal, Iran, and Afghanistan. Countries like India, Pakistan, Bangladesh, Israel, and Myanmar use other traditional calendars too, along with this one. Interestingly, some eastern countries like Japan, Thailand, Taiwan, and North Korea adhere to a modified version of the Gregorian calendar.