Gregorian_calendar

context: To unambiguously specify the date, dual dating or Old Style (O.S.) and New Style (N.S.) are sometimes used with dates. Dual dating uses two consecutive years because of differences in the starting date of the year, or includes both the Julian and Gregorian dates. Old Style and New Style (N.S.) indicate either whether the start of the Julian year has been adjusted to start on 1 January (N.S.) even though documents written at the time use a different start of year (O.S.), or whether a date conforms to the Julian calendar (O.S.) rather than the Gregorian (N.S.).
qas: answers: text: two consecutive years
question: What does duel dating use to show the date?

answers: text: Julian calendar
question: What is the Old Style date mean?

answers: text: New Style
question: What is N.S. stand for?

answers: text: Gregorian
question: What are New Style dates?

answers: text: starting date of the year
question: Why use two consecutive year dates?

context: The Gregorian calendar was a reform of the Julian calendar instituted in 1582 by Pope Gregory XIII, after whom the calendar was named, by papal bull Inter gravissimas dated 24 February 1582. The motivation for the adjustment was to bring the date for the celebration of Easter to the time of year in which it was celebrated when it was introduced by the early Church. Although a recommendation of the First Council of Nicaea in 325 specified that all Christians should celebrate Easter on the same day, it took almost five centuries before virtually all Christians achieved that objective by adopting the rules of the Church of Alexandria (see Easter for the issues which arose).
qas: answers: text: Pope Gregory XIII
question: Who revised the Julian calendar?

answers: text: 1582
question: When was the Gregorian Calendar introduced?

answers: text: Julian calendar
question: What calendar was used in the reform to create the Gregorian calendar?

answers: text: Easter
question: What holiday was the inducement to revise the Julian calendar?

answers: text: on the same day
question: When did the First Council of Nicaea rule that Easter be celebrated by all Christians?

context: Philip II of Spain decreed the change from the Julian to the Gregorian calendar, which affected much of Roman Catholic Europe, as Philip was at the time ruler over Spain and Portugal as well as much of Italy. In these territories, as well as in the Polish–Lithuanian Commonwealth (ruled by Anna Jagiellon) and in the Papal States, the new calendar was implemented on the date specified by the bull, with Julian Thursday, 4 October 1582, being followed by Gregorian Friday, 15 October 1582. The Spanish and Portuguese colonies followed somewhat later de facto because of delay in communication.
qas: answers: text: Philip II of Spain
question: What ruler decreed the change to the Gregorian calendar?

answers: text: Spain and Portugal
question: Besides part of Italy, over what areas did Phillip rule?

answers: text: Friday, 15 October 1582
question: What was the first day selected to be the first day using the new calendar?

answers: text: Thursday, 4 October 1582
question: What was the last day the Julian calendar was used?

answers: text: delay in communication
question: Why did the Spanish colonies lag behind in adopting the calendar?

context: During the period between 1582, when the first countries adopted the Gregorian calendar, and 1923, when the last European country adopted it, it was often necessary to indicate the date of some event in both the Julian calendar and in the Gregorian calendar, for example, "10/21 February 1750/51", where the dual year accounts for some countries already beginning their numbered year on 1 January while others were still using some other date. Even before 1582, the year sometimes had to be double dated because of the different beginnings of the year in various countries. Woolley, writing in his biography of John Dee (1527–1608/9), notes that immediately after 1582 English letter writers "customarily" used "two dates" on their letters, one OS and one NS.
qas: answers: text: 1923
question: When did the last country to adopt the Gregorian calendar start using it?

answers: text: 1582
question: At what date did the first country start using the new calendar?

answers: text: in both
question: How which calendar did some countries notate the date?

answers: text: Woolley
question: Who said that English writers usually used both dates on writings?

answers: text: different beginnings of the year
question: What difference in dating caused the use of double-dating documents?

context: The calendar was a refinement to the Julian calendar amounting to a 0.002% correction in the length of the year. The motivation for the reform was to bring the date for the celebration of Easter to the time of the year in which it was celebrated when it was introduced by the early Church. Because the celebration of Easter was tied to the spring equinox, the Roman Catholic Church considered the steady drift in the date of Easter caused by the year being slightly too long to be undesirable. The reform was adopted initially by the Catholic countries of Europe. Protestants and Eastern Orthodox countries continued to use the traditional Julian calendar and adopted the Gregorian reform after a time, for the sake of convenience in international trade. The last European country to adopt the reform was Greece, in 1923.
qas: answers: text: 0.002%
question: What was the percentsge of correction from the Julian calendar to the new Gregorian calendar?

answers: text: length of the year
question: What was the correction due to?

answers: text: celebration of Easter
question: What change in date motivated the change in calendars?

answers: text: spring equinox
question: To what astrological date was Easter tied?

answers: text: slightly too long
question: What was wrong in the Julian calendar?

context: The Gregorian calendar is a solar calendar. A regular Gregorian year consists of 365 days, but as in the Julian calendar, in a leap year, a leap day is added to February. In the Julian calendar a leap year occurs every 4 years, but the Gregorian calendar omits 3 leap days every 400 years. In the Julian calendar, this leap day was inserted by doubling 24 February, and the Gregorian reform did not change the date of the leap day. In the modern period, it has become customary to number the days from the beginning of the month, and February 29th is often considered as the leap day. Some churches, notably the Roman Catholic Church, delay February festivals after the 23rd by one day in leap years.
qas: answers: text: solar
question: What kind of calendar is the Gregorian calendar?

answers: text: 365
question: How many days are in the Gregorian calendar?

answers: text: every 4 years
question: How often is a leap day added to the Julian calendar year?

answers: text: every 400 years
question: When does the Gregorian calendar omit 3 leap days?

answers: text: 24 February
question: On what day did both the Julian and Gregorian calendars add leap day?

context: Easter was the Sunday after the 15th day of this moon, whose 14th day was allowed to precede the equinox. Where the two systems produced different dates there was generally a compromise so that both churches were able to celebrate on the same day. By the 10th century all churches (except some on the eastern border of the Byzantine Empire) had adopted the Alexandrian Easter, which still placed the vernal equinox on 21 March, although Bede had already noted its drift in 725—it had drifted even further by the 16th century.
qas: answers: text: 15th day
question: When was Easter Sunday celebrated after the equinox?

answers: text: compromise
question: What did churches do to settle the date if there was a difference? 

answers: text: 10th century
question: By what century had almost all churches begun celebrating Easter according to the Alexandrian Easter?

answers: text: eastern border
question: On what border of the Byzantine Empire were the last holdouts for celebrating according the  Alexandrian Easter?

answers: text: vernal equinox
question: What date placement drifted increasingly off the true date on the calendar?

context: Lilius's proposals had two components. Firstly, he proposed a correction to the length of the year. The mean tropical year is 365.24219 days long. As the average length of a Julian year is 365.25 days, the Julian year is almost 11 minutes longer than the mean tropical year. The discrepancy results in a drift of about three days every 400 years. Lilius's proposal resulted in an average year of 365.2425 days (see Accuracy). At the time of Gregory's reform there had already been a drift of 10 days since the Council of Nicaea, resulting in the vernal equinox falling on 10 or 11 March instead of the ecclesiastically fixed date of 21 March, and if unreformed it would drift further. Lilius proposed that the 10-day drift should be corrected by deleting the Julian leap day on each of its ten occurrences over a period of forty years, thereby providing for a gradual return of the equinox to 21 March.
qas: answers: text: length of the year
question: What did Lilius first propose to correct in the calendar?

answers: text: 11 minutes
question: By how much is the Julian calendar too long?

answers: text: three days
question: How much difference does the extra 11 minutes make over 400 years time?

answers: text: 21 March
question: On what date was the original vernal equinox set?

answers: text: 10 or 11 March
question: By the time of Lilius where was the equinox falling?

context: Most Western European countries changed the start of the year to 1 January before they adopted the Gregorian calendar. For example, Scotland changed the start of the Scottish New Year to 1 January in 1600 (this means that 1599 was a short year). England, Ireland and the British colonies changed the start of the year to 1 January in 1752 (so 1751 was a short year with only 282 days) though in England the start of the tax year remained at 25 March (O.S.), 5 April (N.S.) till 1800, when it moved to 6 April. Later in 1752 in September the Gregorian calendar was introduced throughout Britain and the British colonies (see the section Adoption). These two reforms were implemented by the Calendar (New Style) Act 1750.
qas: answers: text: 1 January
question: On what date did most European countries set the start of the new year?

answers: text: 1600
question: When did Scotland begin to use January 1 as the start of the new year?

answers: text: 1752
question: When did the other British states and colonies set the year start date to January 1?

answers: text: Calendar (New Style) Act 1750
question: What act did Britain use to implement the use of the Gregorian calendar?

answers: text: 1800
question: When did England finally change the tax year to 6 April?

context: Extending the Gregorian calendar backwards to dates preceding its official introduction produces a proleptic calendar, which should be used with some caution. For ordinary purposes, the dates of events occurring prior to 15 October 1582 are generally shown as they appeared in the Julian calendar, with the year starting on 1 January, and no conversion to their Gregorian equivalents. For example, the Battle of Agincourt is universally considered to have been fought on 25 October 1415 which is Saint Crispin's Day.
qas: answers: text: caution
question: Attempting to use Gregorian dates for earlier events  on the Julian calendar should be used with what action?

answers: text: 25 October 1415
question: When was the Battle of Agincourt?

answers: text: prior to 15 October 1582
question: When are events usually shown as they appeared on the Julian calendar?

answers: text: Saint Crispin's Day
question: What other date is 25 October known for, that keeps the Battle of Agincourt on 25 October,1415?

answers: text: 1 January
question: In the Julian calendar when is the start of the new year?

context: A language-independent alternative used in many countries is to hold up one's two fists with the index knuckle of the left hand against the index knuckle of the right hand. Then, starting with January from the little knuckle of the left hand, count knuckle, space, knuckle, space through the months. A knuckle represents a month of 31 days, and a space represents a short month (a 28- or 29-day February or any 30-day month). The junction between the hands is not counted, so the two index knuckles represent July and August.
qas: answers: text: language-independent
question: Why would a knuckle -space count be used to determine months?

answers: text: 31
question: A knuckle count is a month of how many days?

answers: text: short month
question: The space between knuckles is what kind of month?

answers: text: one's two fists
question: What are held together for a knuckle-space month count?

context: The Gregorian reform contained two parts: a reform of the Julian calendar as used prior to Pope Gregory XIII's time and a reform of the lunar cycle used by the Church, with the Julian calendar, to calculate the date of Easter. The reform was a modification of a proposal made by Aloysius Lilius. His proposal included reducing the number of leap years in four centuries from 100 to 97, by making 3 out of 4 centurial years common instead of leap years. Lilius also produced an original and practical scheme for adjusting the epacts of the moon when calculating the annual date of Easter, solving a long-standing obstacle to calendar reform.
qas: answers: text: two parts
question: How many parts did the Gregorian calendar reform have?

answers: text: Julian calendar
question: What was the first reform concerning the calendar?

answers: text: lunar cycle
question: What was the second reform of the calendar?

answers: text: date of Easter
question: What was calculated using the lunar calendar?

answers: text: number of leap years
question: What did Lilius's calendar plan to reduce in every 400 years?

context: Prior to 1917, Turkey used the lunar Islamic calendar with the Hegira era for general purposes and the Julian calendar for fiscal purposes. The start of the fiscal year was eventually fixed at 1 March and the year number was roughly equivalent to the Hegira year (see Rumi calendar). As the solar year is longer than the lunar year this originally entailed the use of "escape years" every so often when the number of the fiscal year would jump. From 1 March 1917 the fiscal year became Gregorian, rather than Julian. On 1 January 1926 the use of the Gregorian calendar was extended to include use for general purposes and the number of the year became the same as in other countries.
qas: answers: text: lunar Islamic
question: What calendar did Turkey use before 1917 for general purposes?

answers: text: Julian
question: What calendar did Turkey utilize for fiscal purposes?

answers: text: 1 March
question: Where did Turkey start the fiscal year?

answers: text: 1 March 1917
question: When did Turkey begin to use the Gregorian calendar for fiscal means?

answers: text: 1 January 1926
question: When did Turkey start using the Gregorian calendar for all purposes?

context: Up to February 28 in the calendar you are converting from add one day less or subtract one day more than the calculated value. Remember to give February the appropriate number of days for the calendar you are converting into. When you are subtracting days to move from Julian to Gregorian be careful, when calculating the Gregorian equivalent of February 29 (Julian), to remember that February 29 is discounted. Thus if the calculated value is -4 the Gregorian equivalent of this date is February 24.
qas: answers: text: subtract one day
question: How many days do you subtract to convert days from a calendar?

answers: text: February 29 is discounted
question: What does one need to remember about  the date of February 29 in the Julian calendar?

answers: text: -4
question: If you need a date of four days less, what do you subtract from the Julian calendar?

context: In addition to the change in the mean length of the calendar year from 365.25 days (365 days 6 hours) to 365.2425 days (365 days 5 hours 49 minutes 12 seconds), a reduction of 10 minutes 48 seconds per year, the Gregorian calendar reform also dealt with the accumulated difference between these lengths. The canonical Easter tables were devised at the end of the third century, when the vernal equinox fell either on 20 March or 21 March depending on the year's position in the leap year cycle. As the rule was that the full moon preceding Easter was not to precede the equinox the equinox was fixed at 21 March for computational purposes and the earliest date for Easter was fixed at 22 March. The Gregorian calendar reproduced these conditions by removing ten days.
qas: answers: text: 10 minutes 48 seconds
question: What is the difference in time between the calendars?

answers: text: accumulated difference
question: With what other difference did the Gregorian calendar concern itself?

answers: text: 20 March or 21 March
question: When was the vernal equinox at the end of the third century?

answers: text: 22 March
question: In order to account for the full moon coming after the equinox, when was the equinox set?

answers: text: removing ten days
question: How did the Gregorian calendar set these same of the full moon not preceding Easterconditions?

context: The Council of Trent approved a plan in 1563 for correcting the calendrical errors, requiring that the date of the vernal equinox be restored to that which it held at the time of the First Council of Nicaea in 325 and that an alteration to the calendar be designed to prevent future drift. This would allow for a more consistent and accurate scheduling of the feast of Easter. In 1577, a Compendium was sent to expert mathematicians outside the reform commission for comments. Some of these experts, including Giambattista Benedetti and Giuseppe Moleto, believed Easter should be computed from the true motions of the sun and moon, rather than using a tabular method, but these recommendations were not adopted. The reform adopted was a modification of a proposal made by the Calabrian doctor Aloysius Lilius (or Lilio).
qas: answers: text: 1563
question: When did the Council of Trent agree to the corrected calendar?

answers: text: 325
question: To what time did the Council require the date of the vernal equinox to be set?

answers: text: motions of the sun and moon
question: What did mathematicians of the time want to use to set the date of Easter?

answers: text: tabular method
question: What method was used instead of computations of the sun and moon?

answers: text: Aloysius Lilius
question: Whose modified proposal was adopted?

context: A month after having decreed the reform, the pope with a brief of 3 April 1582 granted to Antonio Lilio, the brother of Luigi Lilio, the exclusive right to publish the calendar for a period of ten years. The Lunario Novo secondo la nuova riforma printed by Vincenzo Accolti, one of the first calendars printed in Rome after the reform, notes at the bottom that it was signed with papal authorization and by Lilio (Con licentia delli Superiori... et permissu Ant(onii) Lilij). The papal brief was later revoked, on 20 September 1582, because Antonio Lilio proved unable to keep up with the demand for copies.
qas: answers: text: 3 April 1582
question: When were the rights to publish the calendar granted?

answers: text: the pope
question: Who awarded the rights to publish the calendar?

answers: text: demand for copies
question: What problem caused the papal brief granting the right to publish to be withdrawn?

answers: text: 20 September 1582
question: When were the rights to print the calendar withdrawn?

answers: text: Rome
question: Where were the first calendars printed?

context: The year used in dates during the Roman Republic and the Roman Empire was the consular year, which began on the day when consuls first entered office—probably 1 May before 222 BC, 15 March from 222 BC and 1 January from 153 BC. The Julian calendar, which began in 45 BC, continued to use 1 January as the first day of the new year. Even though the year used for dates changed, the civil year always displayed its months in the order January to December from the Roman Republican period until the present.
qas: answers: text: consular year
question: What year did the Roman Republic use for dates?

answers: text: consuls first entered office
question: What event started the consular year?

answers: text: 1 May
question: What was the date of the consular year before 222 BC?

answers: text: 15 March
question: What was the date of the start of the consular year from 222 BC?

answers: text: 45 BC
question: When did Rome begin to use the Julian calendar?

context: In conjunction with the system of months there is a system of weeks. A physical or electronic calendar provides conversion from a given date to the weekday, and shows multiple dates for a given weekday and month. Calculating the day of the week is not very simple, because of the irregularities in the Gregorian system. When the Gregorian calendar was adopted by each country, the weekly cycle continued uninterrupted. For example, in the case of the few countries that adopted the reformed calendar on the date proposed by Gregory XIII for the calendar's adoption, Friday, 15 October 1582, the preceding date was Thursday, 4 October 1582 (Julian calendar).
qas: answers: text: system of weeks
question: What other system of calculations are inherent in the Gregorian calendar?

answers: text: irregularities
question: Why is calculating the days of the Gregorian calendar not simple?

answers: text: uninterrupted
question: After each country adopted the calendar how did the weekly cycle continue?

answers: text: Thursday, 4 October 1582
question: What was the previous day's date by the Julian calendar?

answers: text: Friday, 15 October 1582
question: What was the date of adoption for the calendar?

context: Because the spring equinox was tied to the date of Easter, the Roman Catholic Church considered the seasonal drift in the date of Easter undesirable. The Church of Alexandria celebrated Easter on the Sunday after the 14th day of the moon (computed using the Metonic cycle) that falls on or after the vernal equinox, which they placed on 21 March. However, the Church of Rome still regarded 25 March as the equinox (until 342) and used a different cycle to compute the day of the moon. In the Alexandrian system, since the 14th day of the Easter moon could fall at earliest on 21 March its first day could fall no earlier than 8 March and no later than 5 April. This meant that Easter varied between 22 March and 25 April. In Rome, Easter was not allowed to fall later than 21 April, that being the day of the Parilia or birthday of Rome and a pagan festival.The first day of the Easter moon could fall no earlier than 5 March and no later than 2 April.
qas: answers: text: Roman Catholic Church
question: Who thought that the seasonal drift in the date of Easter unacceptable?

answers: text: spring equinox
question: What even is tired to the date for Easter?

answers: text: Metonic cycle
question: What did the Church of Alexandria use to calculate the date of Easter?

answers: text: 21 March
question: Where did the Church of Alexandria place the vernal equinox?

answers: text: 25 March
question: Until 342 when did the Church of Rome think the vernal equinox fell?

context: Ancient tables provided the sun's mean longitude. Christopher Clavius, the architect of the Gregorian calendar, noted that the tables agreed neither on the time when the sun passed through the vernal equinox nor on the length of the mean tropical year. Tycho Brahe also noticed discrepancies. The Gregorian leap year rule (97 leap years in 400 years) was put forward by Petrus Pitatus of Verona in 1560. He noted that it is consistent with the tropical year of the Alfonsine tables and with the mean tropical year of Copernicus (De revolutionibus) and Reinhold (Prutenic tables). The three mean tropical years in Babylonian sexagesimals as the excess over 365 days (the way they would have been extracted from the tables of mean longitude) were 14,33,9,57 (Alphonsine), 14,33,11,12 (Copernicus) and 14,33,9,24 (Reinhold). All values are the same to two places (14:33) and this is also the mean length of the Gregorian year. Thus Pitatus' solution would have commended itself to the astronomers.
qas: answers: text: Christopher Clavius
question: Who was the architect of the Gregorian calendar?

answers: text: discrepancies
question: What did the architects of the calendar notice about the astronomical tables?

answers: text: Petrus Pitatus
question: Whose solution to the discrepancies of the tables would have been agreeable to astronomers?

answers: text: 1560
question: When did Pitatus offer his solution to the leap year problem?

answers: text: Gregorian leap year rule
question: What is the theory about leap year called?

context: "Old Style" (OS) and "New Style" (NS) are sometimes added to dates to identify which system is used in the British Empire and other countries that did not immediately change. Because the Calendar Act of 1750 altered the start of the year, and also aligned the British calendar with the Gregorian calendar, there is some confusion as to what these terms mean. They can indicate that the start of the Julian year has been adjusted to start on 1 January (NS) even though contemporary documents use a different start of year (OS); or to indicate that a date conforms to the Julian calendar (OS), formerly in use in many countries, rather than the Gregorian calendar (NS).
qas: answers: text: "Old Style" (OS) and "New Style"
question: What designation was added to British dates to differentiate them from countries not using the new calendar? 

answers: text: 1750
question: When was the Calendar act enacted?

answers: text: Gregorian calendar
question: With what did the Calendar Act align the British calendar?

answers: text: confusion
question: What did the use of Old Style and New Style cause?

answers: text: Calendar Act of 1750
question: What law did the British make to cause the use of the Gregorian calendar?

context: The Gregorian calendar improves the approximation made by the Julian calendar by skipping three Julian leap days in every 400 years, giving an average year of 365.2425 mean solar days long. This approximation has an error of about one day per 3,300 years with respect to the mean tropical year. However, because of the precession of the equinoxes, the error with respect to the vernal equinox (which occurs, on average, 365.24237 days apart near 2000) is 1 day every 7,700 years, assuming a constant time interval between vernal equinoxes, which is not true. By any criterion, the Gregorian calendar is substantially more accurate than the 1 day in 128 years error of the Julian calendar (average year 365.25 days).
qas: answers: text: Julian
question: The Gregorian calendar is an improvement over what other calendar?

answers: text: three Julian leap days
question: How many days must be skipped to align the calendar with mean solar days in a year?

answers: text: one day
question: What is the approximate error for every 3,300 years?

answers: text: 1 day
question: What is the error rate of the vernal equinox per every 7,700 years?

answers: text: 1 day in 128 years
question: What was the error rate in the Julian calendar?