Which calendar is correct, Julian or Gregorian? What calendar do we live by?

Since 46 BC, in most countries of the world, it has been used Julian calendar. However, in 1582, by the decision of Pope Gregory XIII, it was replaced by Gregorian. That year, the next day after the fourth of October was not the fifth, but the fifteenth of October. Now the Gregorian calendar is officially adopted in all countries except Thailand and Ethiopia.

Reasons for adopting the Gregorian calendar

The main reason for introducing new system chronology began to move the day of the vernal equinox, depending on which the date of the celebration of Christian Easter was determined. Due to discrepancies between the Julian and tropical calendars (the tropical year is the period of time during which the sun completes one cycle of changing seasons), the day of the vernal equinox gradually shifted to earlier dates. At the time of the introduction of the Julian calendar, it fell on March 21, both according to the accepted calendar system and in fact. But by the 16th century, the difference between the tropical and Julian calendars was already about ten days. As a result, the day of the vernal equinox no longer fell on March 21, but on March 11.

Scientists paid attention to the above problem long before the adoption of the Gregorian chronology system. Back in the 14th century, Nikephoros Grigora, a scientist from Byzantium, reported this to Emperor Andronicus II. According to Grigora, it was necessary to revise the calendar system that existed at that time, since otherwise the date of Easter would continue to shift further and further. late time. However, the emperor did not take any action to eliminate this problem, fearing protest from the church.

Subsequently, other scientists from Byzantium also spoke about the need to switch to a new calendar system. But the calendar continued to remain unchanged. And not only because of the rulers’ fear of causing indignation among the clergy, but also because the further the Christian Easter moved away, the less chance it had of coinciding with the Jewish Passover. This was unacceptable according to church canons.

By the 16th century, the problem had become so urgent that the need to solve it was no longer in doubt. As a result, Pope Gregory XIII assembled a commission, which was tasked with carrying out all the necessary research and creating a new calendar system. The results obtained were displayed in the bullet “Among the most important”. It was she who became the document with which the adoption of the new calendar system began.

The main disadvantage of the Julian calendar is its lack of accuracy in relation to the tropical calendar. In the Julian calendar, all years that are divisible by 100 without a remainder are considered leap years. As a result, the difference with the tropical calendar increases every year. Approximately every century and a half it increases by 1 day.

The Gregorian calendar is much more accurate. It has fewer leap years. In this chronology system, leap years are considered to be years that:

1. divisible by 400 without remainder;
2. divisible by 4 without a remainder, but not divisible by 100 without a remainder.

Thus, the years 1100 or 1700 in the Julian calendar are considered leap years because they are divisible by 4 without a remainder. In the Gregorian calendar, from those that have already passed since its adoption, 1600 and 2000 are considered leap years.

Immediately after the introduction of the new system, it was possible to eliminate the difference between the tropical and calendar years, which at that time was already 10 days. Otherwise, due to errors in calculations, an extra year would accumulate every 128 years. In the Gregorian calendar, an extra day occurs only every 10,000 years.

Not in all of them modern states the new chronology system was adopted immediately. The Catholic states were the first to switch to it. In these countries, the Gregorian calendar was officially adopted either in 1582 or shortly after the decree of Pope Gregory XIII.

In a number of states, the transition to a new calendar system was associated with popular unrest. The most serious of them took place in Riga. They lasted for five whole years - from 1584 to 1589.

There were also some funny situations. So, for example, in Holland and Belgium, due to the official adoption of the new calendar, after December 21, 1582, January 1, 1583 came. As a result, the inhabitants of these countries were left without Christmas in 1582.

Russia was one of the last to adopt the Gregorian calendar. The new system was officially introduced on the territory of the RSFSR on January 26, 1918 by decree of the Council of People's Commissars. In accordance with this document, immediately after January 31 of that year, February 14 came on the territory of the state.

Later than in Russia, the Gregorian calendar was introduced only in a few countries, including Greece, Turkey and China.

After the official adoption of the new chronology system, Pope Gregory XIII sent a proposal to Constantinople to switch to new calendar. However, she was met with refusal. Its main reason was the inconsistency of the calendar with the canons of celebrating Easter. However, later most Orthodox churches switched to the Gregorian calendar.

Today, only four Orthodox churches use the Julian calendar: Russian, Serbian, Georgian and Jerusalem.

Rules for specifying dates

In accordance with the generally accepted rule, dates falling between 1582 and the moment the Gregorian calendar was adopted in the country are indicated in both the old and new styles. In this case, the new style is indicated in quotation marks. Earlier dates are indicated according to the proleptic calendar (i.e., a calendar used to indicate dates earlier than the date the calendar appeared). In countries where the Julian calendar was adopted, dates before 46 BC. e. are indicated according to the proleptic Julian calendar, and where there was none - according to the proleptic Gregorian calendar.

Julian calendar IN Ancient Rome from the 7th century BC e. A lunisolar calendar was used, which had 355 days, divided into 12 months. The superstitious Romans were afraid of even numbers, so each month consisted of 29 or 31 days. New Year started on March 1st.

In order to bring the year as close as possible to the tropical one (365 and ¼ days), an additional month was introduced every two years - marcedonia (from the Latin "marces" - payment), initially equal to 20 days. This month should have been the end of all cash payments for the past year. However, this measure failed to eliminate the discrepancy between the Roman and tropical years. Therefore, in the 5th century. BC e. Marcedonium began to be administered twice every four years, alternating 22 and 23 additional days. Thus, average year in this 4-year cycle was equal to 366 days and became longer than the tropical year by approximately ¾ days. Using your right to enter into the calendar additional days and months, the Roman priests - pontiffs (one of the priestly colleges) confused the calendar so much that in the 1st century. BC e. There is an urgent need for its reform.

Such a reform was carried out in 46 BC. e. on the initiative of Julius Caesar. The reformed calendar became known as the Julian calendar in his honor. The Alexandrian astronomer Sosigenes was invited to create a new calendar. The reformers faced the same task - to bring the Roman year as close as possible to the tropical one and thereby maintain constant correspondence of certain days of the calendar with the same seasons.

The Egyptian year of 365 days was taken as a basis, but it was decided to introduce an additional day every four years. Thus, the average year in a 4-year cycle became equal to 365 days and 6 hours. The number of months and their names remained the same, but the length of the months was increased to 30 and 31 days. An additional day began to be added to February, which had 28 days, and was inserted between the 23rd and 24th, where marcedonium had previously been inserted. As a result, in such an extended year, a second 24th appeared, and since the Romans kept count of the day in an original way, determining how many days remained until a certain date of each month, this additional day turned out to be the second sixth before the March calendar (before March 1). In Latin, such a day was called "bis sectus" - the second sixth ("bis" - twice, also "sexto" - six). In Slavic pronunciation, this term sounded slightly different, and the word “leap year” appeared in Russian, and the elongated year began to be called a leap year.

In Ancient Rome, in addition to the calends, special names were given to the fifth days of each short (30 day) month or the seventh of a long (31 day) month - nones and the thirteenths of a short or fifteenth long month - ides.

January 1 began to be considered the beginning of the new year, since on this day the consuls and other Roman magistrates began to perform their duties. Subsequently, the names of some months were changed: in 44 BC. e. Quintilis (fifth month) began to be called July in honor of Julius Caesar in 8 BC. e. Sextilis (sixth month) - August in honor of Emperor Octavian Augustus. Due to the change in the beginning of the year, the ordinal names of some months lost their meaning, for example, the tenth month (“December” - December) became the twelfth.

The new Julian calendar took on the following form: January (“Januaris” - named after the two-faced god Janus); February (“februarius” – month of purification); March (“martius” – named after the god of war Mars); April (“Aprilis” – probably got its name from the word “Apricus” – warmed by the sun); May (“Mayus” – named after the goddess Maya); June (“Junius” – named after the goddess Juno); July (“Julius” – named after Julius Caesar); August (“Augustus” – named after Emperor Augustus); September (“September” – seventh); October (“October” – eighth); November (“November” – ninth); December (“december” – tenth).

So, in the Julian calendar, the year became longer than the tropical one, but by an amount significantly less than the Egyptian year, and was shorter than the tropical year. If the Egyptian year was ahead of the tropical year by one day every four years, then the Julian year was behind the tropical one by one day every 128 years.

In 325, the first Ecumenical Council of Nicaea decided to consider this calendar mandatory for all Christian countries. The Julian calendar is the basis of the calendar system that most countries in the world now use.

In practice, a leap year in the Julian calendar is determined by the divisibility of the last two digits of the year by four. Leap years in this calendar are also years whose designations have zeros as the last two digits. For example, among the years 1900, 1919, 1945 and 1956, 1900 and 1956 were leap years.

Gregorian calendar In the Julian calendar, the average length of the year was 365 days 6 hours, therefore, it was longer than the tropical year (365 days 5 hours 48 minutes 46 seconds) by 11 minutes 14 seconds. This difference, accumulating annually, led after 128 years to an error of one day, and after 1280 years to 10 days. As a result, the spring equinox (March 21) at the end of the 16th century. fell on March 11, and this threatened in the future, provided that the equinox on March 21 was preserved, by moving the main holiday of the Christian church, Easter, from spring to summer. According to church rules, Easter is celebrated on the first Sunday after the spring full moon, which falls between March 21 and April 18. Again the need arose for calendar reform. The Catholic Church has implemented new reform in 1582 under Pope Gregory XIII, after whom the new calendar received its name.

A special commission of clergy and astronomers was created. The author of the project was the Italian scientist - doctor, mathematician and astronomer Aloysius Lilio. The reform was supposed to solve two main problems: firstly, to eliminate the accumulated difference of 10 days between the calendar and tropical years, and secondly, to bring the calendar year as close as possible to the tropical one, so that in the future the difference between them would not be noticeable.

The first task was solved administratively: a special papal bull ordered October 5, 1582 to be counted as October 15. Thus, the spring equinox returned to March 21.

The second problem was solved by reducing the number of leap years in order to reduce the average length of the Julian calendar year. Every 400 years, 3 leap years were thrown out of the calendar, namely those that ended centuries, provided that the first two digits of the year designation were not evenly divisible by four. Thus, 1600 remained a leap year in the new calendar, and 1700, 1800 and 1900. became simple, since 17, 18 and 19 are not divisible by four without a remainder.

The new Gregorian calendar created was much more advanced than the Julian calendar. Each year now lagged behind the tropical one by only 26 seconds, and the discrepancy between them in one day accumulated after 3323 years.

Since different textbooks give different figures characterizing the discrepancy of one day between the Gregorian and tropical years, the corresponding calculations can be given. A day contains 86,400 seconds. The difference between the Julian and tropical calendars of three days accumulates after 384 years and amounts to 259,200 seconds (86400*3=259,200). Every 400 years, three days are removed from the Gregorian calendar, i.e., we can consider that the year in the Gregorian calendar decreases by 648 seconds (259200:400=648) or 10 minutes 48 seconds. The average length of the Gregorian year is thus 365 days 5 hours 49 minutes 12 seconds (365 days 6 hours - 10 minutes 48 seconds = 365 days 5 hours 48 minutes 12 seconds), which is only 26 seconds longer than the tropical year (365 days 5 hours 49 minutes 12 seconds – 365 days 5 hours 48 minutes 46 seconds = 26 seconds). With such a difference, the discrepancy between the Gregorian calendar and the tropical years in one day will occur only after 3323 years, since 86400:26 = 3323.

The Gregorian calendar was initially introduced in Italy, France, Spain, Portugal and the Southern Netherlands, then in Poland, Austria, the Catholic states of Germany and in several other European countries. In those states where the Orthodox Christian Church dominated, for a long time used the Julian calendar. For example, in Bulgaria a new calendar was introduced only in 1916, in Serbia in 1919. In Russia, the Gregorian calendar was introduced in 1918. In the 20th century. the difference between the Julian and Gregorian calendars had already reached 13 days, so in 1918 it was prescribed to count the day following January 31 not as February 1, but as February 14.

There are no problems with measuring certain quantities. When it comes to length, volume, weight - no one has any disagreements. But as soon as you touch the dimension of time, you will immediately encounter different points vision. Special attention should be paid to what the Julian and Gregorian calendars are; the difference between them has really changed the world.

Difference between Catholic and Orthodox holidays

It's no secret that Catholics celebrate Christmas not on January 7, like the Orthodox, but on December 25. The situation is the same with other Christian holidays.

A whole series of questions arises:

• Where did these 13 days difference come from?
• Why can't we celebrate the same event on the same day?
• Will the 13 day difference ever change?
• Maybe it will shrink over time and disappear altogether?
• At least find out what all this is connected with?

To answer these questions we will have to mentally travel to pre-Christian Europe. However, there was no talk of any kind of integral Europe at that time; civilized Rome was surrounded by many disparate barbarian tribes. Subsequently, they were all captured and became part of the Empire, but that's another conversation.

However, history is written by the victors, and we will never know to what extent “ barbaric"were neighbors of Rome. It's no secret that great rulers have a hand in all events in the state. Julius Caesar was no exception when I decided to introduce a new calendar - Julian .

What calendars did you use and for how long?

The ruler cannot be denied modesty, but he made too much of a contribution to the history of the whole world to be criticized over trifles. His proposed calendar:

1. It was much more accurate than previous versions.
2. All years consisted of 365 days.
3. Every fourth year there was 1 more day.
4. The calendar was consistent with astronomical data known at that time.
5. For one and a half thousand years, not a single worthy analogue has been proposed.

But nothing stands still; at the end of the 14th century, a new calendar was introduced, and the then pope, Gregory XIII, contributed to this. This version of the countdown boiled down to the fact that:

• A normal year has 365 days. A leap year contains the same 366.
• But now not every fourth year was considered a leap year. Now if the year ends with two zeros, and at the same time divisible by both 4 and 100, it is not a leap year.
• For a simple example, 2000 was a leap year, but 2100, 2200 and 2300 will not be leap years. Unlike 2400.

Why was it necessary to change something, was it really impossible to leave everything as it was? The fact is that, according to astronomers, The Julian calendar is not entirely accurate.

The error is only 1/128 of a day, but over 128 years a whole day accumulates, and over five centuries - almost four full days.

How does the Julian calendar differ from the Gregorian calendar?

Fundamental differences between the two calendars are that:

• Julian was adopted much earlier.
• It lasted 1000 years longer than the Gregorian.
• Unlike the Gregorian calendar, the Julian calendar is now almost never used anywhere.
• The Julian calendar is used only for calculating Orthodox holidays.
• The Gregorian calendar is more accurate and avoids minor errors.
• The calendar adopted by Gregory XIII is presented as the final version, absolutely correct system reference that will not change in the future.
• In the Julian calendar, every 4th year is a leap year.
• In Gregorian, years that end in 00 and are not divisible by 4 are not leap years.
• Almost every century ends with the difference between the two calendars increasing by another day.
• The exception is centuries divisible by four.
• According to the Gregorian calendar it is celebrated church holidays Almost all Christians in the world are Catholics, Protestants, Lutherans.
• According to Julian Orthodox Christians celebrate, guided by apostolic instructions.

What could an error of several days lead to?

But is it really so important to maintain this precision; maybe it’s better to pay tribute to traditions? What terrible thing will happen if in five centuries the calendar shifts by 4 days, is it noticeable?

Moreover, those who decide to make changes will certainly not live to see the days when “ wrong“The calculation option will differ by at least a day.

Just imagine that already in February the weather warms up and the first flowering begins. But despite all this, the ancestors describe February as a harsh and frosty winter month.

At this point there may already be a slight misunderstanding about what is happening to nature and the planet? Especially if in November there are snowdrifts instead of fallen leaves. And in October, the variegated foliage on the trees is not pleasing to the eye, because all of it has been rotting on the ground for a long time. This seems insignificant at first glance, when the error is only 24 hours in 128 years.

But calendars regulate, among other things, the most important events in the life of many civilizations - sowing and harvesting. The more accurately all adjustments are made, the more O Larger food supplies will be available next year.

Of course, now this is not so important, in an era of rapid development of scientific and technological progress. But once upon a time it was a matter of life and death for millions of people.

Significant differences between calendars

Distinguishing between the two calendars:

1. More accurate measurement using Gregorian.
2. Irrelevance of the Julian calendar: except Orthodox Church almost no one uses it.
3. The universal use of the Gregorian calendar.
4. By removing the 10 day lag and introducing a new rule - all years ending in 00 and not divisible by 4 are now not leap years.
5. Thanks to this, the difference between calendars is steadily increasing. For 3 days every 400 years.
6. Julian was adopted by Julius Caesar, still 2 thousand years ago.
7. Gregorian is more “young”, it is not even five hundred years old. And Pope Gregory XIII introduced it.

What are the Julian and Gregorian calendars, the difference between them and the reasons for their introduction can be known for general development. IN real life this information will never be useful. Unless you want to impress someone with your erudition.

Video about the differences between Gregorian and Julian

In this video, Priest Andrei Shchukin will talk about the main differences between these two calendars from the point of view of religion and mathematics:

In Europe, starting in 1582, the reformed (Gregorian) calendar gradually spread. The Gregorian calendar provides a much more accurate approximation of the tropical year. The Gregorian calendar was first introduced by Pope Gregory XIII in Catholic countries on October 4, 1582, replacing the previous one: the next day after Thursday, October 4, became Friday, October 15.
The Gregorian calendar (“new style”) is a time calculation system based on the cyclic 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.

Difference between 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 differences in the rules for determining leap years. Therefore, when determining which date of the “new calendar” a particular date of the “old calendar” falls on, it is necessary to take into account the century in which the event took place. For example, if in the 14th century this difference was 8 days, then in the 20th century it was already 13 days.

This follows the distribution of leap years:

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

Thus, 1600 and 2000 were leap years, but 1700, 1800 and 1900 were not leap years. Also, 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 approximately 10 thousand years (in the Julian calendar - approximately in 128 years).

Time of approval of the Gregorian calendar

The Gregorian calendar, adopted in most countries of the world, was not put into use immediately:
1582 - Italy, Spain, Portugal, Poland, France, Lorraine, Holland, Luxembourg;
1583 - Austria (part), Bavaria, Tyrol.
1584 - Austria (part), Switzerland, Silesia, Westphalia.
1587 - Hungary.
1610 - Prussia.
1700 - Protestant German states, Denmark.
1752 - Great Britain.
1753 - Sweden, Finland.
1873 - Japan.
1911 - China.
1916 - Bulgaria.
1918 - Soviet Russia.
1919 - Serbia, Rumania.
1927 - Türkiye.
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 Council of People's Commissars replaced the traditional Julian calendar with the Gregorian calendar. As stated in the Decree of the Council of People's Commissars, this decision was made “in order to establish in Russia the same calculation of time with almost all cultural peoples.” In accordance with the decree, the dates of all obligations were considered to have occurred 13 days later. Until July 1, 1918, a kind of transition period was established when it was allowed to use the old style calendar. But at the same time, the document clearly established the order of writing old and new dates: it was necessary to write “after the date of each day according to the new calendar, in brackets the number according to the calendar that was still in force.”

Events and documents are dated with a double date in cases where it is necessary to indicate 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)

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 according to the old style

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

(amendment + 13 days to the Julian calendar)

2019 non-leap

IN 2019 Orthodox Easter falls on April 15(according to the Julian calendar)

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

Disadvantages of the Julian calendar

In 325 AD e. The Nicene Church Council took place. It adopted the Julian calendar for the entire Christian world, according to which at that time the spring equinox fell on March 21. For the church it was important point in determining the time of Easter celebration - one of the most important religious holidays. By accepting the Julian calendar, the clergy believed that it was perfectly accurate. However, as we know, for every 128 years an error of one day accumulates.

An error in the Julian calendar led to the fact that the actual time of the vernal equinox no longer coincides with the calendar. The moment of equality between day and night moved to earlier and earlier dates: first to March 20, then to 19, 18, etc. By the second half of the 16th century. the error was 10 days: according to the Julian calendar, the moment of the equinox was supposed to occur on March 21, but in reality it already occurred on March 11.

History of the Gregorian reform.

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

The inaccuracy of the Julian calendar was also pointed out by the Greek scientist Matvey 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 some “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 scientist Isaac Argir, who more deeply understood the need to correct the Julian calendar and the rules for calculating Easter, considered such an event useless. The reason for this attitude towards the calendar was explained by the fact that Argir was deeply confident in the coming “doomsday” and the end of the world in 119 years, since it would be 7000 years “since the creation of the world.” Is it worth it to reform the calendar if there is so little time left for the life of all humanity!

The need to reform the Julian calendar was also understood by many representatives of the Catholic Church. In the 14th 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 Paschals were the subject of discussion at the Council of Basel in March 1437. Here, the outstanding philosopher and scientist of the Renaissance, Nicholas of Cusa (1401-1464), one of the predecessors of Copernicus, came up with his project.

In 1475, Pope Sixtus IV began preparations for the reform of the calendar and the correction of Easter. For this purpose, he invited the outstanding 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 16th century Two more “ecumenical” councils dealt with issues of calendar reform: the Lateran (1512-1517) and the Trent Council (1545-1563). When in 1514 the Lateran Council created a commission to reform the calendar, the Roman Curia invited the then well-known Polish astronomer Nicolaus Copernicus (1473-1543) in Europe 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 prematureness of such a reform, since, in his opinion, by this time the length of the tropical year had not been established accurately enough.

Gregorian reform. By the middle of the 16th century. the question of calendar reform became so widespread and the importance of its solution turned out to be so necessary that postponing this issue further was considered undesirable. That is why in 1582 Pope Gregory XIII created special commission, which included Ignatius Danti (1536-1586), a well-known professor of astronomy and mathematics at the University of Bologna at that time. This commission was tasked with developing a draft of a new calendar system.

After reviewing all the proposed options for the new calendar, the commission approved the project, the author of which was the Italian mathematician and physician Luigi Lilio (or Aloysius Lilius, 1520-1576), a teacher 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 accepted by Pope Gregory XIII. On February 24, 1582, he issued a special bull (Fig. 11), according to which the count of days was moved forward 10 days and the day after Thursday October 4, 1582, Friday was ordered to be counted not as October 5, but as October 15. This immediately corrected the error that had accumulated since the Council of Nicea, and the spring equinox again fell on March 21.

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

By this time, astronomical tables, known as the “Prussian Tables,” had already been published. They were compiled by the German astronomer and mathematician Erasmus Reinhold (1511-1553) and published in 1551. The length of the year in them was taken to be 365 days 5 hours 49 minutes 16 seconds, i.e. more than the true value of the tropical year by only 30 seconds. The length of the year of the Julian calendar 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 moves ahead by three days every 400 years. Therefore, in order to avoid new errors, it was decided to exclude 3 days from the count 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 century years of the Julian calendar, the number of hundreds in which is not divisible by 4. Thus, in the new calendar, only those century years are considered leap years, the number of centuries of which is divisible by 4 without 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 the Gregorian calendar accurate? We already know that the Gregorian calendar is also not entirely accurate. After all, when correcting the calendar, they began to throw out three days every 400 years, while such an error accumulates 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 of the length of the tropical year by only 0.000305 average day, 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 as simple. Such years could be 4000, 8000, etc. Since the error of the Gregorian calendar is 0.000305 days per year, then in 4000 years it will be 1.22 days. If you correct the calendar for one more day in 4000 years, then an error of 0.22 days will remain. Such an error will increase to a full 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 did not immediately become widespread. In countries where Catholicism was the dominant religion (France, Italy, Spain, Portugal, Poland, etc.), it was introduced in 1582 or slightly later. Other countries recognized it only after tens and hundreds of years.

In states where Lutheranism was strongly developed, for a long time they were guided by the saying that “it is better to separate from the Sun than to get along with the Pope.” 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 of the “calendar riots” that arose in 1584 in Riga and were directed against the decree of the Polish king Stefan Batory on the introduction of a new calendar not only in Poland, but also in the Duchy of Zadvina, 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 riots” stopped only after the leaders of the uprising, Giese and Brinken, were arrested, severely tortured and executed in 1589.

In England, the introduction of a new calendar was accompanied by a postponement of the start of the new year from March 25 to January 1. Thus, the year 1751 in England consisted of only 282 days. Lord Chesterfield, on whose initiative calendar reform was carried out in England, was pursued by the townspeople shouting: “Give us our three months.”

In the 19th 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 in Russia Soviet power, calendar reform was implemented.

The difference between the two calendar systems. By the time of the calendar reform, 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 both according to 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 20th century. - up to 13 days.

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

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

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

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

A special place is occupied by the issue of recalculating 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. Thus, in 1973, humanity 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 to the new style. How was this done?

Since in the 16th century. the difference between the two calendar systems was 10 days, then, knowing the speed with which it changes, it is possible to establish the magnitude of this difference for the various centuries preceding the calendar reform. It should be borne in mind that in 325 the Council of Nicaea adopted the Julian calendar and the spring equinox then fell on March 21. Taking all this into account, we can continue the table. 1 in reverse side and receive the following translation amendments:

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