New calendar style. Old and new style in historical dates. History of the Gregorian Reform

Gregorian calendar

This calculator allows you to convert the date from the Julian to the Gregorian calendar, as well as calculate the date of Orthodox Easter in the old style

* to calculate Easter according to the new style, you must enter the date obtained according to the old style in the calculation form

(amendment + 13 days to the Julian calendar)

2019 year common

V 2019 Orthodox Easter falls on April 15(Julian calendar)

Date calculation Orthodox Easter is performed according to the algorithm of Karl Friedrich Gauss

Disadvantages of the Julian calendar

In 325 A.D. NS. the Nicene Church Council took place. It was adopted for the entire Christian world Julian calendar, according to which at that time the vernal equinox fell on March 21. For the church it was important point in determining the time for celebrating Easter - one of the most important religious holidays. Accepting the Julian calendar, the churchmen believed that it was perfectly accurate. However, as we know, an error of one day accumulates in it every 128 years.

Julian calendar error caused valid time the vernal equinox has ceased to coincide with the calendar. The moment of equality of day and night passed to earlier numbers: first on March 20, then on 19, 18, etc. By the second half of the 16th century. the error was 10 days: according to the Julian calendar, the equinox was supposed to occur on March 21, but in reality it was already on March 11.

History of the Gregorian Reform.

The inaccuracy of the Julian calendar was discovered in the first quarter of the 14th century. So, in 1324, the Byzantine scientist Nikifor Grigora drew the attention of Emperor Andronicus II to the fact that the vernal equinox no longer falls on March 21 and, therefore, Easter will gradually be postponed to a later time. Therefore, he considered it necessary to correct the calendar and together with it the calculation of the Passover. However, the emperor rejected Grigor's proposal, considering the reform practically impracticable due to the impossibility of reaching an agreement on this point between the individual Orthodox churches.

The inaccuracy of the Julian calendar was also pointed out by the Greek scientist Matthew Vlastar, who lived in Byzantium in the first half of the 14th century. However, he did not consider it necessary to make corrections, since he saw in this a certain "advantage", consisting in the fact that the delay of the Orthodox Easter saves it from coinciding with the Jewish Passover. Their simultaneous celebration was prohibited by the decrees of some "Ecumenical" councils and various church canons.

It is interesting to note that in 1373 the Byzantine scholar Isaac Argir, who more deeply understood the need to correct the Julian calendar and the rules for calculating the Paschal, considered such an event useless. The reason for this attitude to the calendar was due to the fact that Argir was deeply convinced of the coming “end of the world” in 119 years and the end of the world, since 7000 years “from the day of the creation of the world” will be celebrated. Is it worth it to reform the calendar if there is so little time left for the life of all mankind!

The need to reform the Julian calendar was understood by many representatives catholic church... In the XIV century. Pope Clement VI spoke in favor of correcting the calendar.

In March 1414 the calendar issue was discussed at the initiative of Cardinal Pierre d'Ailly. The shortcomings of the Julian calendar and the inaccuracy of the existing Easter were the subject of discussion at the Basel Cathedral in March 1437. Here, the outstanding philosopher and scientist of the Renaissance Nikolai of Cusa (1401-1464), one of Copernicus's predecessors, presented his project.

In 1475, Pope Sixtus IV began preparations for the reform of the calendar and the correction of the Passover. For this purpose, he invited the eminent German astronomer and mathematician Regiomontanus (1436-1476) to Rome. However, the unexpected death of the scientist forced the pope to postpone the implementation of his intention.

In the XVI century. two more "ecumenical" councils were involved in the reform of the calendar: Lateran (1512-1517) and Trent (1545-1563). When in 1514 the Lateran Council created a commission for the reform of the calendar, the Roman curia invited the then already famous in Europe Polish astronomer Nicolaus Copernicus (1473-1543) to come to Rome and take part in the work of the calendar commission. However, Copernicus avoided participating in the commission and pointed out the premature of such a reform, since, in his opinion, by this time the duration of the tropical year had not been established sufficiently accurately.

Gregorian reform. TO mid XVI v. the issue of calendar reform was so widespread and the importance of its solution was so necessary that it was considered undesirable to postpone this issue any further. That is why in 1582 Pope Gregory XIII created a special commission, to which he introduced Ignatius Danti (1536-1586), the then famous professor of astronomy and mathematics at the University of Bologna. This commission was charged with developing a draft of a new calendar system.

After reviewing all the proposed versions of the new calendar, the commission approved the project, which was authored by the Italian mathematician and physician Luigi Lilio (or Aloysius Lilius, 1520-1576), a professor of medicine at the University of Perugia. This project was published in 1576 by the scientist's brother, Antonio Lilio, who, during Luigi's lifetime, took an active part in the development of the new calendar.

Lilio's project was adopted by Pope Gregory XIII. On February 24, 1582, he issued a special bull (Fig. 11), according to which the counting of days was moved 10 days ahead and the day after Thursday on October 4, 1582, it was prescribed to count Friday not 5, but 15 October. This immediately corrected the error that had accumulated since the time of the Nicene Council, and the vernal equinox again fell on March 21.

It was more difficult to resolve the issue of introducing such an amendment into the calendar, which would ensure the coincidence of the calendar date of the vernal equinox with its actual date for a long time. To do this, it was necessary to know the length of the tropical year.

By this time, astronomical tables, known as "Prussian tables", had already been published. They were compiled by the German astronomer and mathematician Erasmus Reingold (1511-1553) and published in 1551. The length of the year in them was taken equal to 365 days 5 hours 49 minutes 16 seconds, that is, the more true value of the tropical year by only 30 seconds. The length of the Julian calendar year differed from it by 10 minutes. 44 sec. per year, which gave an error per day for 135 years, and for 400 years - slightly more than three days.

Consequently, the Julian calendar goes forward by three days every 400 years. Therefore, in order to avoid new mistakes, it was decided to throw out 3 days from the account every 400 years. According to the Julian calendar, there should be 100 leap years in 400 years. To implement the reform, it was necessary to reduce their number to 97. Lilio proposed to consider as simple those secular years of the Julian calendar, the number of hundreds in which is not divisible by 4. Thus, in the new calendar, only those secular years, the number of centuries of which is divisible by 4 without the remainder. Such years are: 1600, 2000, 2400, 2800, etc. The years 1700, 1800, 1900, 2100, etc. will be simple.

The reformed calendar system was called the Gregorian or "new style".

Is it accurate Gregorian calendar? We already know that the Gregorian calendar is also not entirely accurate. Indeed, when correcting the calendar, they began to throw out three days in every 400 years, while such an error occurs only in 384 years. To determine the error of the Gregorian calendar, we calculate the average length of the year in it.

In a period of 400 years, there will be 303 years of 365 days and 97 years of 366 days. The total number of days in a four-century period will be 303 × 365 + 97 × 366 == 110 595 + 35 502 = 146 097. Divide this number by 400. Then we get 146097/400 = 365.242500 accurate to the sixth decimal place. This is the average length of a year in the Gregorian calendar. This value differs from the currently accepted value for the length of a tropical year by only 0.000305 average days, which gives a difference of a whole day over 3280 years.

The Gregorian calendar could be improved and made even more accurate. To do this, it is enough to consider one leap year every 4000 years simple. Such years could be 4000, 8000, etc. Since the error of the Gregorian calendar is 0.000305 days per year, then for 4000 years it will be 1.22 days. If the calendar is corrected for one more day of 4000 years, then an error of 0.22 days will remain. This error will increase to a whole day in only 18,200 years! But such accuracy is no longer of any practical interest.

When and where was the Gregorian calendar first introduced? The Gregorian calendar was not immediately generalized. In countries where the dominant religion was Catholicism (France, Italy, Spain, Portugal, Poland, etc.), it was introduced in 1582 or somewhat later. Other countries recognized it only after tens and hundreds of years.

In states where Lutheranism was highly developed, long time were guided by the saying that "it is better to part with the Sun than to get along with dad." The Orthodox Church opposed the new style even longer.

In a number of countries, great difficulties had to be overcome when introducing the Gregorian calendar. History knows the "calendar disturbances" that arose in 1584 in Riga and were directed against the decree of the Polish king Stefan Batory to introduce a new calendar not only in Poland, but also in the Duchy of Zadvin, which was at that time under Lithuanian-Polish domination. The struggle of the Latvian people against Polish dominance and Catholicism continued for several years. The "calendar disturbances" ended only after the leaders of the uprising, Giese and Brinken, were arrested in 1589, brutally tortured and executed.

In England, the introduction of the new calendar was accompanied by the postponement of the beginning of the new year from March 25 to January 1. Thus, 1751 in England consisted of only 282 days. Lord Chesterfield, who initiated the calendar reform in England, was persecuted by the townspeople with shouts: "Give us our three months."

In the XIX century. Attempts were made to introduce the Gregorian calendar in Russia, but each time these attempts failed due to opposition from the church and government. Only in 1918, immediately after the establishment of Soviet power in Russia, the calendar reform was carried out.

The difference between the two calendaring systems. At the time of the reform of the calendar, the difference between the old and new styles was 10 days. This amendment remained the same in the 17th century, since 1600 was a leap year in both the new style and the old one. But in the 18th century. the amendment increased to 11 days, in the 19th century. - up to 12 days and, finally, in the XX century. - up to 13 days.

How to set the date after which the amendment changes its value?

The reason for the change in the value of the amendment depends on the fact that in the Julian calendar 1700, 1800 and 1900 are leap years, that is, these years in February contain 29 days, and in Gregorian they are not leap years and have only 28 days in February.

To translate the Julian date of any event that occurred after the reform of 1582 to new style you can use the table:

It can be seen from this table that the critical days, after which the amendment increases by one day, are February 29 according to the old style of those century years in which, according to the rules of the Gregorian reform, one day was thrown out of the account, i.e. years 1700, 1800, 1900 , 2100, 2200, etc. Therefore, starting from March 1 of these years, again according to the old style, the amendment is increased by one day.

A special place is occupied by the question of recounting the dates of events that took place before the introduction of the Gregorian calendar in the 16th century. Such a recount is also important when they are going to celebrate the anniversary of a historical event. So, in 1973, mankind celebrated the 500th anniversary of the birth of Copernicus. It is known that he was born on February 19, 1473 according to the old style. But we now live according to the Gregorian calendar and therefore it was necessary to recalculate the date of interest to us for a new style. How was this done?

Since in the XVI century. the difference between the two calendar systems was 10 days, then, knowing how fast it changes, you can set the value of this difference for different centuries preceding the reform of the calendar. It should be borne in mind that in 325 the Council of Nicaea adopted the Julian calendar and the vernal equinox then fell on March 21st. Considering all this, we can continue table. 1 in reverse side and get the following translated amendments:

Date interval	Amendment
from 1.III.300 to 29.II.400	0 days
from 1.III.400 to 29.II.500	+ 1 day
from 1.III.500 to 29.II.600	+ 2 days
from 1.III.600 to 29.II.700	+ 3 days
from 1.III.700 to 29.II.900	+ 4 days
from 1.III.900 to 29.II.1000	+ 5 days
from 1.III.1000 to 29.II.1100	+ 6 days
from 1.III.1100 to 29.II.1300	+ 7 days
from 1.III.1300 to 29.II.1400	+ 8 days
from 1.III.1400 to 29.II.1500	+ 9 days
from 1.III.1500 to 29.II.1700	+ 10 days

From this table it can be seen that for the date February 19, 1473, the amendment will be +9 days. Consequently, the 500th anniversary of the birth of Copernicus was celebrated on 19 + 9-28 February 1973.

As in other Christian countries, from the end of the 10th century in Russia, the Julian calendar was used, based on observations of visible movement Suns across the sky. Introduced him into Ancient rome Guy Julius Caesar in 46 BC NS.

The calendar was developed by the Alexandrian astronomer Sozigen based on the calendar of Ancient Egypt. When Russia adopted Christianity in the 10th century, the Julian calendar came with it. However, the average length of a year in the Julian calendar is 365 days and 6 hours (i.e. there are 365 days in a year, and an extra day is added every fourth year). While the duration of the astronomical solar year is equal to 365 days 5 hours 48 minutes and 46 seconds. That is, the Julian year was 11 minutes 14 seconds longer than the astronomical year and, therefore, lagged behind the real change of years.

By 1582, the difference between the Julian calendar and the actual change of years was already 10 days.

This led to the reform of the calendar, which was carried out in 1582 by a special commission created by Pope Gregory XIII. The difference was eliminated when, after October 4, 1582, it was ordered to count not October 5, but immediately on October 15. In the name of the pope, the new, reformed calendar came to be called the Gregorian calendar.

In this calendar, unlike the Julian calendar, the ending year of the century, if it is not divisible by 400, is not a leap year. Thus, the Gregorian calendar has 3 leap years less than the Julian calendar every 400 years. The Gregorian calendar retained the name of the months of the Julian calendar, an additional day in a leap year is February 29 and the beginning of the year is January 1.

The transition of the countries of the world to the Gregorian calendar was long. First, the reform took place in Catholic countries (Spain, Italian states, the Commonwealth, a little later in France, etc.), then in Protestant (in Prussia in 1610, in all German states by 1700, in Denmark in 1700, in Great Britain in 1752, in Sweden in 1753). And only in the nineteenth and twentieth centuries the Gregorian calendar was adopted in some Asian (in Japan in 1873, China in 1911, Turkey in 1925) and Orthodox (in Bulgaria in 1916, in Serbia in 1919, in Greece in 1924 year) states.

In the RSFSR, the transition to the Gregorian calendar was carried out by the decree of the Council of People's Commissars of the RSFSR "On the introduction of the Western European calendar in the Russian Republic" dated February 6, 1918 (January 26, old style).

The calendar problem in Russia has been discussed many times. In 1899, the Astronomical Society had a Commission on the Reform of the Calendar in Russia, which included Dmitry Mendeleev and the historian Vasily Bolotov. The Commission proposed to modernize the Julian calendar.

“Taking into account: 1) that in 1830 the petition of the Imperial Academy of Sciences to introduce the Gregorian calendar in Russia was rejected by Emperor Nicholas I and 2) that the Orthodox states and the entire Orthodox population of the East and West rejected the attempts of representatives of Catholicism to introduce the Gregorian calendar in Russia, the Commission unanimously decided to reject all proposals on the introduction of the Gregorian calendar in Russia and, not hesitating to choose a reform, to stop at one that would combine the idea of truth and possible accuracy, both scientific and historical, in relation to the Christian chronology in Russia, "reads Resolution of the Commission on the Reform of the Calendar in Russia from 1900.

So long-term use in Russia, the Julian calendar was due to the position of the Orthodox Church, which treated the Gregorian calendar negatively.

After the church was separated from the state in the RSFSR, the link between the civil calendar and the church calendar lost its relevance.

The difference in calendars created inconveniences in relations with Europe, which was the reason for the adoption of the decree "in order to establish in Russia the same reckoning of time with almost all cultural peoples."

The question of reform was raised in the fall of 1917. One of the projects under consideration proposed a gradual transition from the Julian to the Gregorian calendar, dropping days each year. But, since the difference between the calendars at that time was 13 days, the transition would take 13 years. Therefore, Lenin supported the option of a one-time transition to a new style. The church refused to switch to the new style.

“The first day after January 31 of this year is not considered February 1, but February 14, the second day is considered 15, etc.,” read the first paragraph of the decree. The rest of the paragraphs indicated how to calculate the new deadlines for the fulfillment of any obligations and in what numbers citizens will be able to receive a salary.

The change of dates has created confusion with the celebration of Christmas. Before the transition to the Gregorian calendar in Russia, Christmas was celebrated on December 25, but now it has moved to January 7. As a result of these changes, in 1918 there was no Christmas at all in Russia. In 1917, we celebrated the last Christmas, which fell on December 25. And next time Orthodox holiday was celebrated already on January 7, 1919.

Christmas is the most fabulous, the most magical holiday... A holiday that promises a miracle. The most long-awaited holiday of the year. Christmas is more important than New Year. So it is in the West, and so it was in Russia before the revolution. It is Christmas that is the very warm family holiday with the obligatory Christmas tree and the expectation of gifts from Santa Claus or Santa Claus.

So why do Christians have two Christmases today? Why do Orthodox Christians celebrate Christmas on January 7, and Catholics and Protestants on December 25?

And the point here is not at all in religious discrepancies, but only in the calendar. Initially, the Julian calendar existed in Europe. This calendar appeared before our era and was generally accepted until the 16th century. The Julian calendar was named after Julius Caesar, who introduced the calendar in 45 BC. instead of the outdated Roman calendar. The Julian calendar was developed by a group of Alexandrian astronomers led by Sozigen. Sozigen is an Alexandrian scientist, a scientist from the very Alexandria, which was in the Egyptian lands. He was invited to Rome by Caesar to develop a calendar. He is also known for his philosophical treatises, for example, a commentary on Aristotle's "De Caelo". But his philosophical works have not survived to this day.

The Julian calendar was developed based on the ancient Egyptian knowledge of astronomy. In the Julian calendar, the year begins on January 1, since it was on this day that newly elected consuls took office in Ancient Rome. The year consisted of 365 days and was divided by 12 months. Once every four years there was a leap year, to which one day was added - February 29. But the calendar was not accurate enough. Every 128 years, one extra day accumulated. And Christmas, which in the Middle Ages was celebrated in Western Europe practically on the days of the winter solstice, it began to gradually move away closer and closer to spring. The day of the vernal equinox, by which the date of Easter was determined, was also shifted.

And then the popes came to understand that the calendar is not accurate and needs to be improved. Gregory XIII became the pope who carried out the calendar reform. It was in honor of him that the new calendar was named Gregorian. Before Gregory XIII, Pope Paul III and Pius IV attempted to change the calendar, but their attempts were unsuccessful. The new Gregorian calendar was introduced on October 4, 1582. Astronomers Christopher Clavius and Aloysius Lilius were involved in the development of the calendar on behalf of the Pope. After the introduction of the new calendar in 1582, the date of October 4, Thursday, was immediately followed by a new date - October 15, Friday. This is how the Julian calendar lagged behind the Gregorian by that time.

The Gregorian calendar consists of 365 days a year, a leap year has 366 days. But at the same time, the calculation of leap years has become more perfect. So a leap year is a year whose number is a multiple of 4. Years divisible by 100 are leap years if they are divided by 400. Thus, 2000 was a leap year, 1600 was a leap year, and 1800 or 1900, for example, were not leap years. An error in one day now accumulates over 10,000 years, in Julian - over 128 years.

With every century, the difference in days between the Gregorian and Julian calendar increases by exactly one day.

By 1582, initially unified Christian church has already split into two parts - Orthodox and Catholic. In 1583, Pope Gregory XIII, the head of the Catholic Church, sent an embassy to the head of the Orthodox Church, Patriarch Jeremiah II of Constantinople, with a proposal to also switch to the Gregorian calendar, but he refused.

So it turned out that Catholics and Protestants celebrate Christmas on December 25 according to the new Gregorian calendar, and Orthodox Christians - Russian, Jerusalem, Serbian, Georgian Orthodox churches and Athos - according to the old Julian calendar and also December 25, but which is true in the modern Gregorian calendar falls on January 7.

Constantinople, Antioch, Alexandria, Cyprus, Bulgarian, Romanian, Greek and some other Orthodox churches adopted the New Julian calendar, which is similar to the Gregorian calendar, and just like Catholics celebrate Christmas on December 25.

By the way, in the Russian Orthodox Church there were also attempts to switch to a New Julian calendar similar to the Gregorian. On October 15, 1923, he was introduced to the Russian Orthodox Church by Patriarch Tikhon. This innovation was accepted by the Moscow parishes, but within the Church itself it caused disagreements and on November 8, 1923, by order of Patriarch Tikhon, "it was temporarily postponed."

V Russian Empire even in the 19th and early 20th centuries, the chronology, in contrast to Europe, was carried out according to the Julian calendar. The Gregorian calendar was introduced only after the revolution in 1918 by a decree of the Council of People's Commissars. Then such names as "old style" - the Julian calendar and "new style" - the Gregorian calendar appeared. Christmas began to be celebrated after the New Year. And besides the New Year itself, the Old One also appeared New Year, in general, the same New Year, but according to the old Julian calendar.

Here's a calendar story. Merry Christmas, and maybe Christmas and New Year or New Years. Happy Holidays!

The Russian Orthodox Church uses in liturgical life the Julian calendar (the so-called old style), developed by a group of Alexandrian astronomers led by the famous scientist Sozigen and introduced by Julius Caesar in 45 BC. NS.

After the introduction of the Gregorian calendar in Russia on January 24, 1918, the All-Russian Local Council decided that "during 1918 the Church in her daily life will be guided by the old style."

On March 15, 1918, at a meeting of the Department of Worship, Preaching and the Church, the following decision was made: independent decision his Russian Church, without preliminary communication on this issue with representatives of all autocephalous Churches, to leave the Julian calendar in its entirety in the Russian Orthodox Church. " In 1948, at the Moscow meeting of Orthodox Churches, it was established that Easter, like all rolling church holidays, must be calculated according to the Alexandrian Easter (Julian calendar), and non-moving ones - according to the calendar adopted in the local church. According to the Gregorian calendar, Easter is celebrated only by the Finnish Orthodox Church.

Currently, only a few local Orthodox churches use the Julian calendar: Jerusalem, Russian, Georgian and Serbian. It is also adhered to by some monasteries and parishes in Europe and the United States, the monasteries of Athos and a number of monophysist churches. However, all Orthodox churches that have adopted the Gregorian calendar, except for the Finnish one, still calculate the day of the celebration of Easter and the holidays, the dates of which depend on the date of Easter, according to the Alexandrian Easter and the Julian calendar.

To calculate rolling dates church holidays the calculation is based on the date of Easter, determined by the lunar calendar.

The accuracy of the Julian calendar is low: every 128 years it accumulates an extra day. Because of this, for example, the Nativity of Christ, initially almost coinciding with the winter solstice, is gradually shifting towards spring. For this reason, in 1582 in Catholic countries, the Julian calendar was replaced by a more accurate decree by Pope Gregory XIII. Protestant countries gradually abandoned the Julian calendar.

The difference between the Julian and Gregorian calendars is constantly increasing due to the different rules for determining leap years: in the XIV century it was 8 days, in the XX and XXI centuries- 13, and in the XXII century the gap will be equal to 14 days. Due to the growing change in the difference between the Julian and Gregorian calendars, Orthodox churches using the Julian calendar, starting from 2101, will celebrate Christmas not on January 7 according to the civil (Gregorian) calendar, as in the XX-XXI centuries, but already on January 8, but , for example, since 9001 - already March 1 (new style), although in their liturgical calendar this day will still be marked as December 25 (old style).

For the above reason, one should not confuse the recalculation of the real historical dates of the Julian calendar to the Gregorian calendar style with the recalculation to the new style of the Julian church month dates, in which all the days of the celebrations are fixed as Julian (that is, without taking into account which Gregorian date a particular holiday or memorable day corresponds ). Therefore, to determine the date, for example, of the Nativity of the Virgin in the new style in the 21st century, it is necessary to add 13 by 8 (the Nativity of the Virgin is celebrated according to the Julian calendar on September 8), and in the XXII century already 14 days. The translation to the new style of civil dates is carried out taking into account the century of a specific date. So, for example, the events of the Battle of Poltava took place on June 27, 1709, which, according to the new (Gregorian) style, corresponds to July 8 (the difference between the Julian and Gregorian styles in the 18th century was 11 days), and, for example, the date of the Borodino battle is August 26, 1812 year, and according to the new style it is September 7, since the difference between the Julian and Gregorian styles in the 19th century is already 12 days. Therefore, civil historical events will always be celebrated according to the Gregorian calendar at the time of the year in which they occurred according to the Julian calendar (the Battle of Poltava - in June, the Battle of Borodino - in August, M.V. Lomonosov's birthday - in November, etc.), and the dates church holidays are shifting forward due to their rigid attachment to the Julian calendar, which is quite intensively (on a historical scale) accumulating errors of calculation (in several millennia, the Nativity of Christ will no longer be a winter, but a summer holiday).

For quick and convenient translation of dates between different calendars, it is advisable to use

In Europe, starting in 1582, the reformed (Gregorian) calendar gradually spread. The Gregorian calendar gives a much more accurate approximation to the tropical year. For the first time, the Gregorian calendar was introduced by Pope Gregory XIII in Catholic countries on October 4, 1582, instead of the previous one: the next day after Thursday, October 4, was Friday October 15.
The Gregorian calendar ("new style") is a time reckoning system based on the cyclical revolution of the Earth around the Sun. The length of the year is taken to be 365.2425 days. The Gregorian calendar contains 97 by 400 years.

The difference between the Julian and Gregorian calendars

At the time of the introduction of the Gregorian calendar, the difference between it and the Julian calendar was 10 days. However, this difference between the Julian and Gregorian calendars gradually increases over time due to the difference in the rules for determining leap years... Therefore, when determining which date of the "new calendar" falls on this or that date of the "old calendar", it is necessary to take into account the century in which the event took place. For example, if in the XIV century this difference was 8 days, then in the XX century it was already 13 days.

Hence the distribution of leap years:

a year whose number is divisible by 400 is a leap year;
the rest of the years, the number of which is a multiple of 100, are non-leap years;
the rest of the years, the number of which is a multiple of 4, are leap years.

Thus, 1600 and 2000 were leap years, while 1700, 1800 and 1900 were not leap years. Also, the year 2100 will not be a leap year. An error of one day compared to the year of the equinoxes in the Gregorian calendar will accumulate in about 10 thousand years (in the Julian - in about 128 years).

Time of approval of the Gregorian calendar

The Gregorian calendar, adopted in most countries of the world, was not immediately introduced into use:
1582 - Italy, Spain, Portugal, Poland, France, Lotarangia, Holland, Luxembourg;
1583 - Austria (part), Bavaria, Tyrol.
1584 - Austria (part), Switzerland, Silesia, Westphalia.
1587 - Hungary.
1610 - Prussia.
1700 - Protestant German states, Denmark.
1752 - United Kingdom.
1753 - Sweden, Finland.
1873 - Japan.
1911 - China.
1916 - Bulgaria.
1918 - Soviet Russia.
1919 - Serbia, Roumania.
1927 - Turkey.
1928 - Egypt.
1929 - Greece.

Gregorian calendar in Russia

As you know, until February 1918, Russia, like most Orthodox countries, lived according to the Julian calendar. The "new style" of chronology appeared in Russia in January 1918, when the Soviet People's Commissars replaced the traditional Julian calendar with the Gregorian. As stated in the Decree of the Council of People's Commissars, this decision was made "in order to establish in Russia the reckoning of time that is the same with almost all cultural peoples." In accordance with the decree, the deadlines for all obligations were considered to have occurred 13 days later. Until July 1, 1918, a kind of transitional period was established when it was allowed to use the chronology according to the old style. But at the same time, the document clearly established the order of writing old and new dates: it was necessary to write "after the number of each day according to the new calendar, in brackets the number according to the calendar that was still in force."

The double date is used to date events and documents in cases where it is required to specify the old and new styles. For example, for anniversaries, major events in all works of a biographical nature and dates of events and documents on history international relations associated with countries where the Gregorian calendar was introduced earlier than in Russia.

New Style Date (Gregorian Calendar)