Differences between the Gregorian and Julian calendars

The calendar is one of the inventions with the greatest impact on the life of man, since it is governed by time, in seconds, minutes, hours, days, weeks, months and years, which are contained in the calendar. Throughout the history of humanity, different civilizations have designed calendars to organize time based on the different climatic cycles, the movement of the earth and the changes of seasons, among others.

In the same sense, two of the most popular calendars in the history of man are the Julian calendar and the Gregorian calendar, which we will describe below to later show their most relevant differences.

Julian calendar

The Julian calendar was introduced by Emperor Julius Caesar in 46 BC and was the predominant calendar in the Roman world and in most of Europe. Later, it was progressively replaced by the Gregorian calendar, however, in Orthodox countries it was maintained until the beginning of the 20th century. Currently, in some countries whose official calendar is the Gregorian, the Orthodox Church still uses the Julian calendar.

On the other hand, the Julian calendar has a year of 365 days divided into 12 months, to which a day is added to February every four years (leap year), therefore, the Julian calendar has an average of 365.25 days. In the original Julian calendar the months of July and August were called “quintilis” and “sextilis” respectively and their names were progressively changed in honor of Julius Caesar and Octavian Augustus, Roman emperors.

Since the Julian calendar has a duration of 365.25 days, it was a little longer than the astronomical year and over time errors began to accumulate, so reforms and modifications had to be made to adapt the calendar year. to the astronomical year, thus achieving coincidences in the dates of certain events such as the solstices and equinoxes.

Gregorian calendar

The Gregorian calendar was introduced by Pope Gregory XIII in Europe in the year 1582 and managed to replace by decree the Julian calendar that governed the time in Europe for that date. The Gregorian calendar distinguishes three types of years: the common year that contains 365 days, the leap year that has 366 days, and the secular year that is the year that closes a century (multiples of one hundred).

A defining feature of the Gregorian calendar is that secular years divisible by 400 are leap years, but secular years not divisible by 400 are not leap years. Despite all these corrections, which have the sole purpose of adapting to the real astronomical year, the Gregorian calendar is 26 seconds longer than the astronomical year. This means that there is a difference every 3323 years, so the secular years 4000, 8000 and 16000 will not be leap years even though they correspond to them because they are multiples of 400. According to these figures, the Gregorian calendar in terms of duration of the year in terms of days, is 365, 2425.

As can be seen, there are notable differences between the Julian calendar and the Gregorian calendar, which are detailed in the following table:

Julian calendar Gregorian calendar
It was introduced by Julius Caesar in 46 BC. It was introduced by Pope Gregory XIII in the year 1582.
The year has a duration of 365.25. The year has a duration of 365.2425.
Distinguish between common year and leap year. Distinguish between common year, leap year and secular year

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