Julian calendar. "Creounity Time Machine" - universal date converter

Calendar Celebration of the Kazan Icon Mother of God(in memory of the deliverance of Moscow and Russia from the Poles in 1612) Yuri Ruban, Candidate of Historical Sciences, Candidate of Theology, Associate Professor of St. Petersburg State University

Calendar Yury Ruban, Candidate of Historical Sciences, Candidate of Theology, Associate Professor of St. Petersburg State University Orthodox calendar(December, according to the new style, according to which we really live), you involuntarily linger on the name of the Apostle Andrew (December 13). As in

Calendar One of the most terrible things is diaries, electronic reminders and e-mail. The day of the funeral, and Tolik's calendar pops up a reminder to pay for a trip to the sea. The next morning after the funeral, a letter arrives confirming the reservation for the beloved

We use the calendar all our lives. This seemingly simple table of numbers with the days of the week is very ancient and rich history. Civilizations known to us already then knew how to divide the year into months and days. For example, in ancient Egypt, based on the laws of the movement of the moon and Sirius, a calendar was created. The year was approximately 365 days and was divided into twelve months, which, in turn, were divided into thirty days.

Innovator Julius Caesar

Around 46 BC. e. there was a transformation of the chronology. Roman emperor Julius Caesar created the Julian calendar. It was slightly different from the Egyptian one: the fact is that instead of the Moon and Sirius, the sun was taken as the basis. Now the year was 365 days and six hours. The beginning of the new time was considered the first of January, but Christmas began to be celebrated on January 7th.

In connection with this reform, the senate decided to thank the emperor by naming one month after him, which we know as "July". After the death of Julius Caesar, the priests began to confuse months, the number of days - in a word, the old calendar no longer looked like a new one. Every third year was considered a leap year. From 44 to 9 BC there were 12 leap years, which was not true.

After the emperor Octavian Augustus came to power, there were no leap years for sixteen years, so everything fell into place, and the situation with the chronology improved. In honor of Emperor Octavian, the eighth month was renamed from Sextilis to August.

When the question arose about the appointment of the celebration of Easter day, disagreements began. It was this question that was decided at the Ecumenical Council. The rules that were established at this Council, no one has the right to change to this day.

Innovator Gregory XIII

In 1582, Gregory XIII replaced the Julian calendar with the Gregorian one.. The movement of the vernal equinox was main reason changes. It was according to him that the day of Easter was calculated. At the time when the Julian calendar was introduced, March 21 was considered this day, but around the 16th century the difference between the tropical and Julian calendar was about 10 days, therefore, March 21 was replaced by 11.

In 1853, in Constantinople, the Council of the Patriarchs criticized and condemned the Gregorian calendar, according to which the Catholic bright resurrection was celebrated before the Jewish Passover, which was contrary to the established rules of the Ecumenical Councils.

Differences between old and new style

So, how is the Julian calendar different from the Gregorian?

• Unlike the Gregorian, the Julian was adopted much earlier and is 1,000 years older.
• On the this moment the old style (Julian) is used to calculate the celebration of Easter among Orthodox Christians.
• The chronology created by Gregory is much more accurate than the previous one and will not be subject to change in the future.
• A leap year in the old style is every fourth year.
• In Gregorian, leap years are not those years that are divisible by four and end in two zeros.
• According to the new style, all church holidays are celebrated.

As we can see, the difference between the Julian calendar and the Gregorian one is obvious not only in terms of calculations, but also in terms of popularity.

Rises interest Ask. What calendar are we living on now?

The Russian Orthodox Church uses the Julian, which was adopted during the Ecumenical Council, while the Catholics use the Gregorian. Hence the difference in the dates of the celebration of the Nativity of Christ and Easter. Orthodox Christians celebrate Christmas on January 7, following the decision of the Ecumenical Council, and Catholics on December 25.

These two chronologies have received names - the old and the new style of the calendar.

The area where the old style is used is not very large: the Serbian, Georgian, Jerusalem Orthodox Churches.

As we can see, after the introduction of the new style, the life of Christians around the world has changed. Many gladly accepted the changes and began to live according to it. But there are also those Christians who are faithful to the old style and live according to it even now, albeit in very small numbers.

There will always be disagreements between Orthodox and Catholics, and this is not connected with the old or new style of reckoning. Julian and Gregorian calendars - the difference is not in faith, but in the desire to use one or another calendar.

The Roman calendar was one of the least accurate. At first, it generally had 304 days and included only 10 months, starting from the first month of spring (March) and ending with the onset of winter (Dekember - the “tenth” month); In winter, time was simply not kept. King Numa Pompilius is credited with introducing two winter months(January and February). An additional month - mercedoniy - was inserted by the pontiffs at their own discretion, quite arbitrarily and in accordance with various momentary interests. In 46 BC. e. Julius Caesar carried out a reform of the calendar, according to the development of the Alexandrian astronomer Sosigen, taking the Egyptian solar calendar as a basis.

In order to correct the accumulated errors, he, by his power as the great pontiff, inserted in the transitional year, in addition to mercedony, two additional months between November and December; and from January 1, 45, the Julian year was set at 365 days, from leap years every 4 years. At the same time, an extra day was inserted between February 23 and 24, as earlier mercedony; and since, according to the Roman system of reckoning, the day of February 24 was called “the sixth (sextus) from the March calends,” the intercalary day was also called “twice the sixth (bis sextus) from the March calends” and the year, respectively, annus bissextus - hence, through the Greek language, our word "leap". At the same time, the month of quintiles (in Julius) was renamed in honor of Caesar.

In the IV-VI centuries, in most Christian countries, uniform Easter tables were established, made on the basis of the Julian calendar; thus, the Julian calendar spread throughout christianity. In these tables, March 21 was taken as the day of the vernal equinox.

However, as the error accumulated (1 day in 128 years), the discrepancy between the astronomical spring equinox and the calendar became more and more pronounced, and many in Catholic Europe believed that it could no longer be ignored. This was noted by the Castilian king of the 13th century Alphonse X the Wise, in the next century the Byzantine scholar Nicephorus Gregory even proposed a reform of the calendar. In reality, such a reform was carried out by Pope Gregory XIII in 1582, based on the project of the mathematician and physician Luigi Lilio. in 1582: the day after October 4th was October 15th. Secondly, a new, more precise rule about a leap year began to operate in it.

Julian calendar was developed by a group of Alexandrian astronomers led by Sosigenes and introduced by Julius Caesar in 45 BC. uh..

The Julian calendar was based on the culture of ancient Egyptian chronology. In Ancient Russia, the calendar was known as the "Peaceful Circle", "Church Circle" and "Great Indiction".

The year according to the Julian calendar begins on January 1, since it was on this day from 153 BC. e. newly elected consuls took office. In the Julian calendar, a regular year has 365 days and is divided into 12 months. Once every 4 years, a leap year is announced, to which one day is added - February 29 (previously a similar system was adopted in the zodiac calendar according to Dionysius). Thus, the Julian year has an average duration of 365.25 days, which is 11 minutes different from the tropical year.

The Julian calendar is commonly referred to as the old style.

The calendar was based on static monthly holidays. Kalends were the first holiday with which the month began. The next holiday, falling on the 7th (in March, May, July and October) and on the 5th of the remaining months, were nons. The third holiday, falling on the 15th (in March, May, July and October) and the 13th of the remaining months, was the Ides.

Removal by the Gregorian calendar

In Catholic countries, the Julian calendar was replaced by a decree of Pope Gregory XIII with the Gregorian calendar in 1582: the day after October 4, October 15 came. The Protestant countries abandoned the Julian calendar gradually, over the course of the 17th-18th centuries (the last were Great Britain from 1752 and Sweden). In Russia, the Gregorian calendar has been used since 1918 (it is usually called the new style), in Orthodox Greece - since 1923.

In the Julian calendar, a year was a leap year if it ended in 00. 325 AD. The Council of Nicaea decreed this calendar for all Christian countries. 325 g is the day of the spring equinox.

Gregorian calendar was introduced by Pope Gregory XIII on October 4, 1582 to replace the old Julian: the day after Thursday, October 4 became Friday, October 15 (there are no days from October 5 to October 14, 1582 in the Gregorian calendar).

In the Gregorian calendar, the length of the tropical year is 365.2425 days. The length of a non-leap year is 365 days, a leap year is 366.

Story

The reason for the adoption of the new calendar was the shift of the vernal equinox, which determined the date of Easter. Before Gregory XIII, Popes Paul III and Pius IV tried to implement the project, but they did not achieve success. The preparation of the reform at the direction of Gregory XIII was carried out by the astronomers Christopher Clavius ​​and Luigi Lilio (aka Aloysius Lily). The results of their work were recorded in a papal bull, named after the first line of lat. Inter gravissimas ("Among the most important").

Firstly, the new calendar immediately at the time of adoption shifted the current date by 10 days due to accumulated errors.

Secondly, a new, more precise rule about a leap year began to operate in it.

A leap year has 366 days if:

Its number is divisible by 4 without a remainder and is not divisible by 100 or

Its number is evenly divisible by 400.

Thus, over time, the Julian and Gregorian calendars diverge more and more: by 1 day per century, if the number of the previous century is not divisible by 4. The Gregorian calendar reflects the true state of affairs much more accurately than the Julian. It gives a much better approximation to the tropical year.

In 1583, Gregory XIII sent an embassy to Patriarch Jeremiah II of Constantinople with a proposal to switch to a new calendar. At the end of 1583, at a council in Constantinople, the proposal was rejected as not in accordance with the canonical rules for celebrating Easter.

In Russia, the Gregorian calendar was introduced in 1918 by a decree of the Council of People's Commissars, according to which, in 1918, January 31 was followed by February 14.

Since 1923, most of the local Orthodox churches, with the exception of the Russian, Jerusalem, Georgian, Serbian and Athos, have adopted a similar to the Gregorian New Julian calendar, coinciding with it until 2800. It was also formally introduced by Patriarch Tikhon for use in the Russian Orthodox Church on October 15, 1923. However, this innovation, although it was accepted by almost all Moscow parishes, generally caused disagreement in the Church, so already on November 8, 1923, Patriarch Tikhon ordered "the universal and mandatory introduction of the new style into church use be temporarily postponed." Thus, the new style was valid in the Russian Orthodox Church for only 24 days.

In 1948 at the Moscow meeting Orthodox churches it was decided that Easter, as well as all passing holidays, should be calculated according to the Alexandrian Paschalia (Julian calendar), and non-passing according to the calendar by which he lives local church. The Finnish Orthodox Church celebrates Easter according to the Gregorian calendar.

Gregorian calendar("new style")

Introduced 1582 AD by Pope Gregory XIII so that the day of the vernal equinox does not "slide" to summer, but corresponds certain day(March 21). On this day, the date of Easter is determined, the correct determination of which is very important for the church.

For a more accurate approximation to the actual length of the year, years whose number is a multiple of 100 are taken as non-leap years (except for multiples of 400); For example, 2000 was a leap year and 1900 was a non-leap year.

Earlier dates are converted using the standard rules for Gregorian leap years.

Attention!
Our converter can convert up to 2400 g.

Julian calendar("old style")

Introduced in 46 BC Julius Caesar and totaled 365 days; leap year was originally every third year. The wrong number of leap years again led to the accumulation of errors, so this rule was corrected by Emperor Augustus: from 8 BC. and before 8 AD additional days of leap years were skipped, and thereafter every fourth year became leap years.

Attention!
Our converter converts earlier dates using the standard rules for Julian leap years.

Roman version julian calendar

Introduced around 750 BC Due to the fact that the number of days in the Roman calendar year was changed by the arbitrary decision of the priests, dates before 8 AD. are not accurate and are for demonstration purposes only.

The chronology was conducted from the foundation of Rome (ab Urbe condita) - 753/754 BC.

Attention!
Our date converter is up to 753 B.C. are not calculated, because in the Roman calendar have no historical meaning.

Month names

The names of the months of the Roman calendar are agreed definitions for the word mensis - month:
m. Januarius; m. Februarius; m. Martius; m. Aprilis; m. majus; m. Junius; m. Julius; m. Augustus; m. September; m. October; m. November; m. December.

The god of time - Janus two-faced and Maya - the goddess of fertile land

The Romans, like us, had 12 months (or rather, it modern world borrowed these months from them, often with names), but their year began in March. The months got their name from the names of gods, people, holidays and just numbers:

Numbers of the month

The date within the month was determined by the phases of the moon. The first day of the month (new moon) was called the Kalendae; The 5th or 7th day of the month (the second phase of the moon) was called Nona (Nonae); The 13th or 15th day of the month (third phase, full moon) was called the Idus. Nones on the 7th, and Ides on the 15th day fell in March, May, July and October, in the remaining months of Nona - on the 5th, and Ides - on the 13th.
For example, August 22, 80 AD. designated as follows: eleven days before the September Kalends (ante diem XI Kalendas Septembres).

The first days of the month were determined by counting the days from the upcoming Nons, then, when the Nons passed, from the Ids, and the last days were determined from the future Kalends. If the day fell on Kalends, Nonas or Ides, then the name of this day was put in abl.pl., for example: February 1st - Kalendis Februariis, March 15th - Idibus Martiis, April 5th - Nonis Aprilibus. The day immediately preceding the Kalends, Nonams or Idams was denoted by the word pridie (the day before) with acc.: January 31 - pridie Kalendas Februarias, March 14 - pridie Idus Martias, April 4 - pridie Nonas Apriles.

Days of the week

Although the division into weeks of seven days itself dates back to ancient Babylon, seven days of the week became the standard around the 3rd century AD. The names of the days of the week were given by celestial bodies:

Julian date is the number of days that have passed since noon on January 1, 4713 BC. This date is arbitrary and was chosen by historians only to harmonize various systems of chronology.

lillian date- this is an astronomical way of measuring time, which counts the number of days that have passed since the introduction of the Gregorian calendar (00:00:00 October 15, 1582).

The date changes at midnight Coordinated Universal Time (UTC). The Lillian date of October 15, 1582 has serial number 1. The Lillian date can be obtained from the Julian date by subtracting 2,299,160.5 and eliminating the decimal fraction from the result.
(c) The basis of the script is taken from the currently non-existent site http://www.24hourtranslations.co.uk/dates.htm

Why introduced a new style?

The Gregorian calendar gives a much more accurate approximation of the actual length of the year. Over the centuries, gradually shifted astronomical days to which agricultural work and religious holidays were tied: spring and autumnal equinox etc.

The main reason for the intervention of the Pope and the adoption of a new calendar was the gradual shift in relation to the Julian calendar of the day of the vernal equinox, which determined the date of Easter. Prior to Gregory XIII, Popes Paul III and Pius IV had already tried to update the calendar, but they were not successful. The preparation of the reform at the direction of Gregory XIII was carried out by the astronomers Christopher Clavius ​​and Aloysius Lily.

In 1583, Gregory XIII sent an embassy to Patriarch Jeremiah II of Constantinople with a proposal to switch to a new calendar. At the end of 1583, at a council in Constantinople, the proposal was rejected as not in accordance with the canonical rules for celebrating Easter.

The transition to the Gregorian calendar resulted in the following changes:

• the new calendar immediately at the time of adoption shifted the current date by 10 days and corrected the accumulated errors;
• in the new calendar, a new, more accurate rule about a leap year began to operate - a leap year, that is, it contains 366 days if:
  1. year number is a multiple of 400 (1600, 2000, 2400);
  2. other years - the year number is a multiple of 4 and not a multiple of 100 (... 1892, 1896, 1904, 1908 ...);
  3. the rules for calculating the Christian Easter were modified.
• Over time, the Julian and Gregorian calendars diverge more and more, by three days every 400 years.

The transition to the Gregorian calendar

In some cases, the transition to the Gregorian calendar was accompanied by serious unrest. For example, when the Polish king Stefan Batory introduced a new calendar in Riga in 1584, local merchants rebelled, claiming that a 10-day shift disrupted their delivery schedules and resulted in significant losses. The rebels destroyed the Riga church and killed several municipal employees. It was only in the summer of 1589 that the "calendar disturbances" were dealt with.

In some countries that switched to the Gregorian calendar, the Julian chronology was subsequently resumed as a result of their accession to other states.

In Britain, which, by decision of King George II, switched to the Gregorian calendar on September 2, 1752, had to shift the date forward not by 10, but by 11 days, since a whole century had already passed since the entry into force of the new calendar in continental Europe and one extra day had accumulated. After the 2nd immediately came September 14th. The subjects were dissatisfied with the decision that made them older. Protests were noticed in the country under the slogan: “Give us back our eleven days!”, which is present in particular on one of the engravings of the Election series created by William Hogarth. At times, riots broke out, sometimes resulting in casualties, for example, in Bristol.

The introduction of the new calendar also had serious financial implications. In 1753 - the first full year according to the Gregorian calendar, the bankers refused to pay taxes, waiting for the required 11 days after the usual due date - March 25th. As a result, the "new financial year" in the UK began only on 6 April. This date has been kept until today, as a symbol of great changes that occurred 250 years ago.

In Sweden decided to switch to the new calendar gradually, canceling leap days from 1700 to 1740. In 1700, the first leap day was abolished. Then the war started and they forgot about the translation. Thus, the country lived according to its own Swedish calendar. In 1711, Charles XII recognized this as impractical and decided to return to the old style and add 2 days in February. Therefore, in Sweden it was February 30, 1712. Only in 1753 a new style was introduced. At the same time, after February 17, March 1 immediately followed.

Some countries switched to a new style in parts, for example, various Swiss cantons adopted calendar reform for almost 120 years!

Revolutionary France introduced its own calendar, "republican" with the chronology from the revolution of 1792. It was also based on the Gregorian, but with its own characteristics. In this calendar, weeks became decades, with 10 days in a decade. The month consisted of three decades. The year consisted of 12 months and 5 non-monthly public holidays(6 in a leap year).

The transition to the Gregorian calendar was unusual in Alaska after its sale by Russia, as there it was combined with the transfer of the date line. Therefore, after Friday, October 5, 1867, according to the old style, another Friday, October 18, 1867, according to the new style, followed.

In 1872, the decision to switch from the traditional (lunisolar) calendar to the Gregorian was made by Japan, so that the day after "the second day of the twelfth month of the fifth year of Meiji" became January 1, 1873, bringing Japan's calendar into line with that of the major Western powers (with the exception of Russia). However, in official documents at the same time, the nengo system continues to be used. For example, the year 1868 could be written as the first year of Meiji, 1912 as Taishō 1, 1926 as Showa 1, 1989 as Heisei 1, and so on. In common practice, however, the chronology from the Nativity of Christ is used according to the "Western calendar" (seireki), which became the main one in Japan during the 20th century.

Korea adopted the Gregorian calendar on January 1, 1896. Although according to accepted calendar the correct numbering of months and days was established, but even in the continuation of 1895-1897, the old numbering of years continued according to the first year of the reign of the Joseon dynasty, according to which 1896 of the Gregorian calendar corresponded to 1392 of Joseon. Then countings of years from various historical events were used, until from 1962 a count of years identical to the Gregorian calendar was established. AT North Korea Since July 8, 1997, a new "Juche reckoning" has been adopted, which is based on the rules of the Gregorian calendar, but the beginning of which is 1912 - the year of Kim Il Sung's birth.

Republic of China officially adopted the Gregorian calendar at its proclamation on January 1, 1912. With the unification of China under the Kuomintang in October 1928, the National Government decreed that the Gregorian calendar would be used from January 1, 1929. Nevertheless, China retained the Chinese tradition of numbering months, and the first year of the proclamation of the Republic of China - 1912 - was appointed as the beginning of the chronology. This system is still used in Taiwan, which considers itself the successor to the Republic of China. After the proclamation in 1949 of the Chinese People's Republic, mainland China continued to use the Gregorian calendar, but the numbering and chronology introduced by the previous government was canceled, and a correspondence was established with the chronology from the Nativity of Christ, adopted both in the USSR, friendly to China, and in the West.

In Russia(on the territory under the control of the Soviets) the Gregorian calendar was introduced by a decree of January 26, 1918 of the Council of People's Commissars, according to which in 1918 after January 31, February 14 will follow. In the territories of the former Russian Empire under the control of others state formations that arose after the fall of the Provisional Government, the dates of the official introduction of the new style are different. So, the Provisional Siberian Government introduced a new style by decree of August 31, 1918, deciding to consider the day of October 1, 1918 as the day of October 14, 1918.

Later in USSR the practice was established to keep the chronology from the revolution of 1917 (for example, 1987 was the "70th year of the VOSR"), but the Gregorian calendar remained the main calendar, the phrase "from the birth of Christ" was replaced by "AD" or "BC".

The last to adopt the Gregorian calendar were Greece in 1924, Turkey in 1926 and Egypt in 1928. Until now, only Ethiopia and Thailand have not switched to the Gregorian calendar.

Religions

Since 1923, most of the local Orthodox churches, with the exception of the Russian, Jerusalem, Georgian and Serbian, have adopted a similar to the Gregorian "new Julian" calendar, more accurate and coinciding with the Gregorian until 2800.

Also the Gregorian calendar was introduced by Patriarch Tikhon for use in the Russian Orthodox Church on October 15, 1923.

Patriarch Tikhon

However, this innovation, although it was accepted by almost all parishes, caused confusion among many hierarchs of the church, which was unnecessary in this difficult time, therefore, already on November 8, 1923, Patriarch Tikhon ordered "the universal and mandatory introduction of a new style into church use is temporarily postponed." Thus, the new style was valid in the Russian Orthodox Church for only 24 days.

In 1948, at the Moscow Conference of Orthodox Churches, it was decided that Easter, like all movable holidays, should be calculated according to the Alexandrian Paschalia (Julian calendar), and non-transitional ones - according to the calendar according to which the Local Church lives.

How to recalculate past dates?

If historians around the world did not agree on how and which calendar to use to date historical events, this would lead to inconsistency and confusion in determining dates.

What are the errors in date conversion?

1. In connection with the transition of countries to the Gregorian calendar at different times, factual errors of perception may occur: for example, it is sometimes said that Inca Garcilaso de la Vega, Miguel de Cervantes and William Shakespeare died on the same day - April 23, 1616. In fact, Shakespeare died 10 days later than Inca Garcilaso, since in Catholic Spain the new style was in effect from the very introduction of his pope, and Great Britain switched to the new calendar only in 1752, and 11 days later than Cervantes (who died on 22 April, but was buried on April 23).
2. There are other kinds of errors when, for some reason, to get the date of a historical event according to the Gregorian calendar, they add the number of days that made up the difference between the calendars at the time the country switched to a new calendar style. That is, they spread the difference in the number of days of calendars into the depths of centuries.

   Our State Duma demonstrated such a mistake by appointing a public holiday on November 4 - the deputies added 13 days to the date of the capture of Kitay-Gorod on October 22, 1612, although the difference between the calendars then was only 10 days. This is not to mention the fact that the Kremlin itself, or rather the Kremlin garrison Polish troops surrendered much later than this date.

   In addition, the State Duma also thoughtlessly appointed some memorable military dates:
   The battle on the ice took place on April 5, 1242, memorable date appointed for April 28 (the difference is again 13 days);
   Victory Day of the Russian regiments led by Grand Duke Dmitry Donskoy over the Mongol-Tatar troops in the Battle of Kulikovo; happened on September 8, 1380, for some reason the date was set for September 21 (13 days);

   Moreover, these errors are selective, most of dates are correctly calculated, which especially emphasizes the negligence of the recalculation of the previously mentioned dates:
   Victory Day of the Russian army under the command of Peter the Great over the Swedes in the Battle of Poltava; happened on June 27, 1709, the date was rightly set for July 8 (11 days);
   Day of the Borodino battle of the Russian army under the command of M. I. Kutuzov with French army; happened on August 26, 1812, the date was correctly set for July 5-7 (12 days);

3. If two countries that switched to a new style in different centuries participated in a historical event, careless historians of both countries can make even more confusion, unknowingly recalculating the old date each in their own way. The same Swedes, the date of the Battle of the Neva (July 15, 1240 according to the Julian calendar) could incorrectly recalculate to July 26 according to the Gregorian calendar (+11 days), and our same unfortunate historians would recalculate to July 28 (+13 days).

To avoid such confusion date translation rules adopted:

• To designate all dates before 1582 AD. the most commonly used is the Julian calendar, introduced from January 1, 45 BC.
• Dates before the introduction of the Julian calendar on January 1, 45 BC. e. are designated by the so-called. proleptic Julian calendar. Proleptic (from the Greek. "anticipating") calendar - a calendar extended for the period before its introduction. Simply put, the dates are calculated according to the Julian calendar, despite the fact that the calendar has not even been invented yet.
• To recalculate dates after 1582 in those countries where the Julian calendar continued to operate at the time of the historical event, the date is recalculated into the Gregorian calendar by adding the number of days by which the calendars differed at the time of the event.
• In regions where the Julian calendar was not used at all, the dating of all events is made according to the proleptic Gregorian calendar (which determines the dating of events according to the rules of the Gregorian calendar before its appearance on October 15, 1582).