When we switched to a new calendar. Difference between Julian and Gregorian calendar

Often, reading a historical article about the events that took place before 1918, we see the following dates: "The battle of Borodino took place on August 26 (September 7), 1812". Why two dates? Which one is correct? What is the difference? Why are these brackets? Not one hundred, or even a thousand people annually puzzle over these questions. But in fact, everything is simple. We will save you, dear readers, from a lot of numbers and calculations, and we will explain everything “on the fingers”.

Well, slower, slower. It's about calendars. Julian calendar- This is the calendar by which Russia lived until 1918. In February 1918 we switched to a "new" style - to Gregorian calendar... In Europe, it began to spread from the 16th century. and was introduced by order of Pope Gregory XIII (hence the Gregorian).

Now let's remember a few rules, knowing which, you will no longer get confused in dates:

1 rule: the dates of all events that occurred before 1918 are written in the old style, and the date in brackets is given in the new - Gregorian - calendar: August 26 (September 7) 1812.

2 rule: if a document written before 1918 fell into your hands, and, accordingly, deprived of recalculation to a new style, you do not need to surf the Internet - you can calculate it yourself. To do this, you need this plate:

from 10/05/1582 to 02/18/1700 - add 10 days.

from 02/19/1700 to 02/18/1800 - add 11 days.

from 02/19/1800 to 02/18/1900 - add 12 days.

from 02/19/1900 to 02/01/1918 - add 13 days.

Let's check ourselves:

Tsar Fyodor Ioannovich was born on March 18, 1584 according to the Julian calendar. We look at the plate - we need to add 10 days. In total, according to the Gregorian calendar, Feodor Ioannovich's birthday is March 28, 1584.

But the Battle of Poltava took place on June 27, 1709. How much should you add? Already 11 days. It turns out on July 8th.

The Julian calendar continues to be used by the Russian Orthodox Church. Civil chronology in Russia is based on the Gregorian calendar. So how do you write dates correctly? historical events? When did the Battle of Borodino take place - on August 26 or September 7? The answer is one, and there can be no other: correctly write the date to which the current calendar at that time corresponded. That is, on August 26th.

In the halls of the Historical Museum and Museum Patriotic War 1812, you can find documents with different dates and check yourself. As you can see, it's simple. Forward to the museum!

God created the world outside of time, the change of day and night, seasons allows people to put their time in order. For this, humanity has invented a calendar, a system of calculating days in a year. The main reason for the transition to another calendar was the disagreement over the celebration of the most important day for Christians - Easter.

Julian calendar

Once upon a time, during the reign of Julius Caesar, in 45 BC. the Julian calendar appeared. The calendar itself was named after the ruler. It was the astronomers of Julius Caesar who created the chronology system, focused on the time of the sequential passage of the equinox by the Sun therefore the Julian calendar was a “solar” calendar.

This system was the most accurate for those times, each year, not counting the leap year, contained 365 days. In addition, the Julian calendar did not contradict the astronomical discoveries of those years. For fifteen hundred years, no one could offer this system a worthy analogy.

Gregorian calendar

However, at the end of the 16th century, Pope Gregory XIII proposed a different chronology system. What was the difference between the Julian and Gregorian calendar, if there was no difference in the number of days for them? Every fourth year was no longer considered a leap year by default, as in the Julian calendar. According to the Gregorian calendar, if a year ended at 00 but was not divisible by 4, it was not a leap year. So 2000 was a leap year, and 2100 will no longer be a leap year.

Pope Gregory XIII was based on the fact that Easter should be celebrated only on Sunday, and according to the Julian calendar, Easter fell on a different day of the week each time. February 24, 1582 the world learned about the Gregorian calendar.

Pope Sixtus IV and Clement VII also advocated the reform. The work on the calendar, among others, was led by the Jesuit Order.

Julian and Gregorian calendars - which one is more popular?

The Julian and Gregorian calendars continued to exist together, but in most countries of the world it is the Gregorian calendar that is used, and the Julian remains for the calculation Christian holidays.

Russia was among the last to adopt the reform. In 1917, immediately after the October Revolution, the "obscurantist" calendar was replaced by a "progressive" one. In 1923 they tried to transfer the Russian Orthodox Church to a “new style”, but even with pressure on His Holiness Patriarch Tikhon, the Church was categorically rejected. Orthodox Christians, guided by the instructions of the apostles, calculate the holidays according to the Julian calendar. Catholics and Protestants count the holidays according to the Gregorian calendar.

The question of calendars is also a theological problem. Despite the fact that Pope Gregory XIII considered an astronomical rather than a religious aspect to be the main issue, later discussions appeared about the correctness of one or another calendar in relation to the Bible. In Orthodoxy, it is believed that the Gregorian calendar violates the sequence of events in the Bible and leads to canonical violations: Apostolic rules do not allow the celebration of Holy Passover before the Jewish Passover. Go to new calendar would mean the destruction of the Passover. Scientist-astronomer Professor E.A. Predtechensky in his work "Church Time: Reckoning and a Critical Review of the Existing Rules for Determining Easter" noted: “This collective work (Editor's note - Easter), in all likelihood of many unknown authors, is executed in such a way that it remains unsurpassed to this day. The later Roman Easter, now adopted by the Western Church, is, in comparison with the Alexandrian, so heavy and awkward that it resembles a popular print next to an artistic depiction of the same object. For all that, this terribly complex and clumsy machine still does not achieve its intended goal. "... In addition, the descent of the Holy Fire at the Holy Sepulcher takes place on Holy Saturday according to the Julian calendar.

Exactly 100 years ago, the Russian Republic lived its first day in a new style. Due to the transition from the Julian calendar to the more accurate Gregorian, which was adopted in most European countries back in the 17th century, the first 13 days of February 1918 simply dropped out of the calendar, and after January 31, February 14 immediately followed. This not only helped to synchronize the national calendar with the calendars of other countries, but also led to the fact that the day of the Great October Revolution in the Soviet Union, despite the name, began to be celebrated on November 7, Pushkin's birthday - in June, although he was born, as you know, May 26, and in mid-January there was an incomprehensible holiday - Old New Year... At the same time, the Russian Orthodox Church still uses the Julian calendar, therefore, for example, Orthodox and Catholics celebrate Christmas on different days.

On January 26, 1918, a decree was adopted, according to which the young Soviet Russian Republic switched to the Gregorian calendar generally accepted in Europe. This led not only to a shift in dates, but also to some amendments in determining leap years. In order to understand where the discrepancy between the two calendars comes from, first consider those natural processes that were used in their development.

Astronomy and calendar

The most common calendars are based on the ratio of the times of three cyclical astronomical processes: the rotation of the Earth around its axis, the rotation of the Moon around the Earth, and the rotation of the Earth itself around the Sun. These three processes lead to well noticeable periodic changes on Earth: the change of day and night, the change in the phases of the moon and the alternation of the seasons, respectively. The ratio of the durations of these time intervals is the basis of the overwhelming number of calendars used by mankind. It is clear that there are other astronomical events that are noticeable to humans on Earth, which occur with a convenient regularity (for example, in Ancient egypt watched the ascent of Sirius, which had the same annual cycle), but using them to develop the calendar is rather an exception.

Of the three indicated intervals, from an astronomical point of view, the easiest way to deal with the shortest of them - the length of the day. Now, for the period of time, on the basis of which, in particular, calendars are compiled, they take the average solar day - that is, the average period of time during which the Earth rotates around its axis relative to the center of the Sun. Solar days are because the center of the Sun is used as a reference point, and averaging a day per year has to be due to the fact that, due to the ellipticity of the Earth's orbit and its perturbation by other celestial bodies, the rotation period of our planet changes with the course of the year, and the longest and longest short days differ from each other by almost 16 seconds.

A method for determining the duration of solar days, which are calculated by the change in the orientation of the Earth relative to the initial position (1) not by a full rotation of 360 degrees to position (2), but by one revolution relative to the center of the Sun to position (3)

Wikimedia commons

The second of the necessary time intervals for the calendar is the year. Of several possible options To determine a one-year interval, the calendar uses a seasonal cycle, which can be observed when looking at the position of the Sun in the sky from Earth, the so-called tropical year. It is determined by the change in the ecliptic coordinates of the Sun, and one annual cycle corresponds to a change of 360 degrees in its ecliptic longitude (that is, its longitudinal position on the celestial sphere, measured from the point vernal equinox, in which the plane of rotation of the Earth around the Sun and the equatorial plane of the Earth intersect). At the same time, the length of the year may vary slightly depending on the choice of the starting point, and, as a rule, the vernal equinox point is chosen as the starting position, because for it the error in determining the length of the year is minimal.

The most common solar calendars today (including the Julian and Gregorian) are based on the ratio of the time of the daily and annual period. This ratio, that is, the duration of the tropical year in days, of course, is not a whole and is 365.2422. And how close the calendar can adjust to this value, its accuracy directly depends.

It is worth noting: despite the fact that the duration of one tropical year is practically constant, due to small perturbations of the Earth's orbit, it still changes slightly. These disturbances are associated with the influence of the celestial bodies closest to the Earth, primarily Mars and Venus, all of them are periodic and have an amplitude of 6 to 9 minutes. The period of each of the disturbances is two or three years, which together give a 19-year nutation cycle. In addition, the duration of the tropical year does not coincide with the time of the Earth's revolution around the Sun (the so-called sidereal year). This is due to the precession of the earth's axis, which leads to the emergence of a difference, which is now about 20 minutes (the length of the sidereal year in days is 365.2564).

The third time interval used to compile calendars is the synodic month. It is counted as the time between two identical phases of the moon (for example, new moons) and is on average 29.5306 solar days. The phases of the moon are determined by the mutual position of the three celestial bodies - the Earth, the Moon and the Sun and, for example, do not correspond to the periodicity of the position of the Moon in the celestial sphere relative to the stars. In addition, like the tropical year, the synodic month varies greatly in length.

Lunar calendars based on the change in the phases of the moon were used quite widely, but in most they were superseded by solar or solar-lunar calendars. This is explained both by the inconvenience of using lunar calendars due to noticeable variations in the length of the month, and by the natural linking of human activity to seasonal weather changes, which can be associated with the position of the Sun in the sky, but not with the phase of the Moon. Today, lunar calendars are mainly used to determine the dates of religious holidays. In particular, the lunar is the Muslim calendar, also according to lunar calendar the dates of the Old Testament Christian holidays, especially Easter, are also determined.

Any calendar is based on attempts to relate at least two of these time intervals. But since any of these relations cannot be represented in the form of an ordinary fraction, it is impossible to draw up an absolutely accurate calendar. You can solve this problem relatively in a simple way, without resorting to any calendars at all, but using only one interval, for example, the length of the day. This is what astronomers suggest doing, for example, who simply count the days starting from a certain point in the past (according to modern calendar, this point corresponds to noon on November 24, 4714 BC). In this case, any time point is determined by the Julian date - a fractional number that corresponds to the number of days that have passed from the start of the countdown.

Wikimedia commons

In the picture above: A method for determining the ecliptic coordinates of a celestial body (for example, the Sun) on the celestial sphere. They are measured from the vernal equinox point.

Julian calendar

But counting the time only by day is still not very convenient, and I want to have time intervals of a larger scale at hand. Even realizing that no calendar will allow one to describe with absolute accuracy the relationship between the duration of a solar day, a tropical year and a synodic month, one can achieve satisfactory accuracy from it. It is in the degree of accuracy in describing the ratio of two of these three intervals that the difference between the Julian calendar and the Gregorian one lies.

Both of these calendars are solar, they are designed to relate the duration of the average solar day and the tropical year. We know that from an astronomical point of view, the duration of a tropical year is approximately 365.2422 days. To compose a calendar, this number must be described in some way so that in each calendar year there is an integer number of days. The easiest way to do this is by varying the length of the year.

The roughest of the acceptable roundings gives 365.25 days, and it is on this that the Julian calendar is built. If, with this rounding of the average length of the year, we divide the year into 365 days, then every four years there will be an error of one day. It is from here that the structure of the calendar appears, in which every fourth year is a leap year, that is, it includes one more day than usual. The full cycle of such a calendar is only four years, which makes it very easy to use.

The Julian calendar was developed by the Alexandrian astronomers, named after Julius Caesar, and introduced in 46 BC. Interestingly, initially, an additional day in a leap year was added not by introducing a new date - February 29, but by duplicating February 24.

Of course, the Julian calendar is far from the first version of the solar calendar. So, the basis for all modern solar calendars was the ancient Egyptian solar calendar. It was reckoned according to the position of the rising Sirius in the sky and included 365 days. And although the Egyptians understood that with such a system of counting, for example, the shift of the dates of the solstices and equinoxes occurs very quickly, for convenience, the length of the year did not change. Therefore, every four years there was a shift by one day, and after 1460 years (this interval was called the Great Year of Sothis), the year returned to its original position.

Moreover, in the very Ancient Rome The Julian calendar replaced the previously used Roman calendar of ten months and 354 days. To match the length of the calendar year with the length of the tropical one, an extra month was added to the year every few years.

The Julian calendar turned out to be much more convenient than the Roman one, but it was still not very accurate. The difference between 365.2422 and 365.25 is still great, so the inaccuracy of the Julian calendar was noticed pretty soon, primarily due to the shift in the date of the vernal equinox. TO XVI century it has already moved 10 days from its starting position established by the Council of Nicea in 325 on March 21st. Therefore, in order to improve the accuracy of the calendar, it was proposed to amend the the existing system from leap years.

Wikimedia commons

A graph of the time shift of the summer solstice depending on the year according to the Gregorian calendar. Years are plotted on the abscissa, and the calculated actual time of the summer solstice in calendar notation (a quarter of a day corresponds to six hours) is plotted on the ordinate.

Gregorian calendar

The new calendar was introduced by Pope Gregory XIII, who issued the Inter gravissimas bull in 1582. For a more accurate correspondence of the calendar year to the tropical, the number of leap years in the new Gregorian calendar compared to the Julian calendar decreased by three for every 400 years. therefore leap years there are no longer those whose ordinal numbers are completely divisible by 100, but at the same time are not divisible by 400. That is, 1900 and 2100 are not leap years, but, for example, 2000 was a leap year.

Taking into account the introduced amendments, the duration of one year in days according to the Gregorian calendar was 365.2425, which is already much closer to the required value of 365.2422 compared to what the Julian calendar proposed. As a result of the proposed amendments, there is a difference of three days between the Julian and Gregorian calendars for 400 years. At the same time, the amendment was carried out according to the shift of the day of the vernal equinox in relation to the date established by the Council of Nicea - March 21, 325, so it was only 10 days (the next day after October 4 in 1582 was immediately October 15), and the zero difference between the calendars corresponds not to the first century AD, and the third.

The transition to a more accurate Gregorian calendar in Europe took place gradually. At first, in the 80s of the XVI century, all Catholic countries switched to the Gregorian calendar, and during the XVII and XVIII centuries - gradually the Protestant states. Despite the fact that the reform of Gregory XIII was a measure of the Counter-Reformation, symbolically subordinating calendar time bull of the Roman pontiff, its objective advantages were too obvious to be resisted for a long time for religious reasons.

In Russia, the process of transition to a revised calendar was somewhat delayed: until 1700, when most European countries already lived according to the Gregorian calendar, the Byzantine chronology was still adopted in the Russian kingdom. In terms of defining leap years, the Byzantine calendar, developed in the 7th century, corresponded to the Julian calendar, but differed in the names of the months, the date of the beginning of the year (September 1) and the starting point of the chronology. If the Julian and Gregorian calendars are considered the starting point on January 1 of the year in which Jesus Christ was born, then in the Byzantine version the time is considered "from the creation of the world", allegedly coming in 5509 BC. (Note that in determining the exact year of Christ's birth, a mistake of several years was probably made, which is why, according to the Julian calendar, this should not be the first year of our era, but 7–5 BC).

Peter I translated Russia into the Julian calendar in 1700. On the one hand, he saw the need to "synchronize" the historical time of Russia with the European, on the other hand, he felt deep distrust of the calendar of the "papists", unwilling to introduce "heretical" Easter. True, the Old Believers never accepted his reforms and are still counting dates according to the Byzantine calendar. The New Believer Orthodox Church switched to the Julian calendar, but at the same time, until the beginning of the 20th century, opposed the introduction of a more accurate Gregorian.

Due to the practical inconvenience in the conduct of international affairs, as a result of the inconsistency between the calendars adopted in Europe and Russian Empire, the question of the transition to the Gregorian calendar was raised, especially during the 19th century, repeatedly. For the first time, such a question was discussed during the liberal reforms of Alexander I, but then it did not reach the official level. The problem of the calendar was raised more seriously in 1830, for this a special committee was even assembled at the Academy of Sciences, but as a result, Nicholas I chose to abandon the reform, agreeing with the arguments of the Minister of Public Education Karl Lieven that the people were not ready to switch to a different calendar system due to lack of education and possible indignation.

"Decree on the introduction of the Western European calendar in the Russian Republic"

The next time, a serious commission on the need to switch to the Gregorian calendar in the Russian Empire was gathered at the very end of the 19th century. The commission was formed under the Russian Astronomical Society, but, despite the participation of prominent scientists, in particular Dmitry Mendeleev, it was still decided to abandon the transition due to the insufficient accuracy of the Gregorian calendar.

At the same time, the commission considered the issue of switching both to the Gregorian calendar and to an even more accurate version, developed by a professor at the University of Dorpat astronomer Johann Heinrich von Medler in 1884. Medler suggested using a calendar with a 128-year cycle containing 31 leap years. Average length years in a day according to such a calendar will be 365.2421875 and an error in one day accumulates over 100 thousand years. However, this project was not adopted either. According to historians, the opinion of the Orthodox Church played a significant role in the rejection of reforms.

Only in 1917, after the October Revolution and the separation of church from state, did the Bolsheviks decide to switch to the Gregorian calendar. By that time, the difference between the two calendars had already reached 13 days. Several options were proposed for the transition to a new style. The first was a gradual transition over 13 years, with an amendment made on one day each year. However, in the end, the second, more radical, option was chosen, according to which in 1918 the first half of February was simply canceled, so that after January 31, February 14 immediately began.

Wikimedia commons

The plot of the shift of the time of the vernal equinox according to the New Julian calendar. Years are plotted on the abscissa, and the calculated actual time of the vernal equinox in calendar notation (a quarter of a day corresponds to six hours) is plotted on the ordinate. The blue vertical line marks the year 1923 when the calendar was developed. The period of time before this date is considered according to the proleptic New Julian calendar, which extends the date to an earlier date.

The Julian calendar and the Orthodox Church

The Russian Orthodox Church continues to use the Julian calendar to this day. The main reason she refuses to switch to the Gregorian calendar is the row anchor church holidays(primarily Easter) to the lunar calendar. To calculate the date of Easter, the Easter system is used, which are based on the comparison of lunar months and tropical years (19 tropical years are quite accurately equal to 235 lunar months).

The transition to the Gregorian calendar, according to representatives of the Russian Orthodox Church, will lead to serious canonical violations. In particular, in some cases, when using the Gregorian calendar, the date of Catholic Easter turns out to be earlier than the Jewish date or coincides with it, which is contrary to the Apostolic rules. After the transition to the Gregorian calendar, Catholics celebrated Easter four times before the Jews (all in the 19th century) and five times at the same time (in the 19th and 20th centuries). In addition, Orthodox priests find other reasons not to switch to the Gregorian calendar, for example, shortening the duration of some fasts.

Moreover, part Orthodox churches at the beginning of the 20th century, it switched to the New Julian calendar - with amendments introduced by the Serbian astronomer Milutin Milankovic (known primarily due to the description of climatic cycles). Milankovitch suggested that instead of subtracting three leap years every 400 years, subtracting seven leap years every 900 years. Thus, full cycle the New Julian calendar is 900 years old, which makes it even more accurate, but also more difficult to use, even in relation to the Gregorian.

Milankovitch's amendments lead to the fact that the date according to the New Julian calendar may differ from the Gregorian one both upward and downward (in the foreseeable future - by no more than one day). IN this moment the dates of the New Julian and Gregorian calendar coincide, and the nearest discrepancy between them will appear only in 2800.

The accuracy of the New Julian calendar results in an accumulation of errors of one day every 43,500 years. This is significantly better than the Gregorian calendar (one day in 3280 years) and, of course, the Julian calendar (one day in 128 years). But, for example, the already mentioned Medler amendments, which were also considered by the Russian Orthodox Church as an alternative to the Julian calendar, make it possible to achieve twice as much accuracy (one day in 100 thousand years), even despite a much shorter cycle of 128 years.

Returning to the question of dating the October Revolution and Pushkin's birthday, it is worth noting that they are dated according to the new style (that is, according to the Gregorian calendar), indicating the date in parentheses according to the old (Julian) style. They do the same in European countries for dating even those events that occurred before the introduction of the Gregorian calendar, using the so-called proleptic Gregorian calendar, that is, extending the Gregorian chronology to the period up to 1582.

The difference between the dates of Catholic and Orthodox Christmas is now fully consistent with the difference between the Julian and Gregorian calendars. Accordingly, after 2100, Orthodox Christmas will shift from January 7 to 8, and the difference in dates will increase by one more day.

Alexander Dubov

When talking about dates, one often comes across a common misconception associated with recalculating dates from the Julian calendar to the Gregorian (from the "old style" to the "new"). A significant proportion of people believe that this difference is always 13 days. In fact, everything is much more complicated and the difference between the calendars changes from century to century.

First of all, it is necessary to explain what caused the appearance of different calendars. The fact is that the Earth makes a full revolution around the Sun not in 365 or 366 days, but in 365 days 5 hours 48 minutes 45.19 seconds (data for the 2000s).

In the Julian calendar, introduced in 45 A.D. and spread throughout Europe, incl. (through Byzantium) - and to Russia, the length of the year is 365 days and 6 hours. "Extra" 6 hours are 1 day - February 29, which is added once every 4 years.

Thus, the Julian calendar is inaccurate, and over time this inaccuracy became apparent when calculating Christian holidays, especially Easter, which should be celebrated on the first Sunday after the vernal equinox.

I drew attention to this problem Catholic Church, and from 1582 the Gregorian calendar was introduced. Pope Gregory XIII on October 5, 1582 issued a bull ordering to count October 5 15. Thus, the difference between the calendars was 10 days in the 16th century.

The Gregorian calendar is based on the following principles:

1. Just like in the Julian calendar, every fourth year is a leap year.
2. Years divisible by 400 (for example, 1600 and 2000) are also leap years.
3. The exception is years that are multiples of 100 and not multiples of 400 (for example, 1700, 1800 and 1900): they are not leap years.

Thus, the discrepancy between the Julian and Gregorian calendar is as follows:

In Russia, the Gregorian calendar was introduced by a decree of the Council of People's Commissars of January 24, 1918. After January 31, 1918, February 14 came.

Thus, most of the time by which it is possible to compile a pedigree (XVII - early XX centuries) in Russia, the Julian calendar was in effect, and all dates require recalculation in accordance with the table above. For example, the 150th anniversary of the abolition of serfdom (manifesto of February 19, 1861) - March 3, 2011.

Currently, the Julian calendar continues to be used by some local Orthodox churches, including the Russian Orthodox Church. A significant part of the Orthodox churches (for example, the Greek) adopted the New Julian calendar, which calculates leap years according to another, slightly more complex model. However, until the XXIX century, there will be no discrepancies between the Gregorian and New Julian calendars.

Different ways of calculating the calendar... A new style of time reckoning was introduced by the Council of People's Commissars - the government of Soviet Russia January 24, 1918 "Decree on the introduction of the Western European calendar in the Russian Republic".

The decree was intended to facilitate "The establishment in Russia of the same reckoning of time with almost all cultural peoples"... Indeed, since 1582, when throughout Europe the Julian calendar was replaced by the Gregorian in accordance with the recommendations of astronomers, the Russian calendar turned out to be 13 days different from the calendars of civilized states.

The fact is that the new European calendar was born through the efforts of the Pope, but the Catholic Pope was not an authority or a decree for the Russian Orthodox clergy, and they rejected the innovation. So we lived for more than 300 years: in Europe New Year, in Russia is still on December 19.

By the decree of the Council of People's Commissars (abbreviation of the Council of People's Commissars) of January 24, 1918, it was ordered that February 1, 1918 be considered February 14 (in parentheses, we note that, according to long-term observations, Russian orthodox calendar, that is, "Old style", is more consistent with the climate of the European part Russian Federation... For example, on March 1, when, according to the old style, it is still deep February, there is no smell of spring, and the relative warming begins from mid-March or its first numbers according to the old style).

Not everyone liked the new style

However, not only Russia rested on the establishment of a Catholic day count, in Greece the "New Style" was legalized in 1924, Turkey - 1926, Egypt - 1928. At the same time, something is not heard that the Greeks or Egyptians celebrated, as in Russia, two holidays: New Year and Old New Year, that is, New Year in the old style.

Interestingly, the introduction of the Gregorian calendar was also accepted without enthusiasm in those European countries where Protestantism was the leading religion. So in England, the time was changed only in 1752, in Sweden - a year later, in 1753.

Julian calendar

Introduced by Julius Caesar in 46 BC. Started on January 1st. The year had 365 days. The year number divisible by 4 was recognized as a leap year. One day was added to it - February 29. The difference between the calendar of Julius Caesar and the calendar of Pope Gregory is that the first has every fourth year, without exception, a leap year, and the second has leap years only those years that are divisible by four, but not multiples of one hundred. As a result, the difference between the Julian and Gregorian calendars is gradually increasing and, for example, in 2101 An Orthodox xmas will not be celebrated on January 7, but on January 8.