The Ultimate Leap Year Quiz

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How many years out of the 400-year cycle are leap years?

97 (correct)

303

366

365

What was the motivation for the Gregorian calendar reform?

To bring the date of Easter closer to the spring equinox (correct)

To align the calendar with the lunar cycle

To adjust for the precession of the equinoxes

To bring the date of Christmas closer to the winter solstice

Who instituted the Gregorian calendar reform?

Pope Gregory V

Pope Gregory XIII (correct)

Pope Gregory IV

Pope Gregory III

What was the error in the Julian calendar that led to the Gregorian calendar reform?

Assumption of 365.25 days in a year Signup and view all the answers

Who estimated the accumulated error of the Julian calendar to be seven or eight days in the 13th century?

Roger Bacon Signup and view all the answers

Which council recommended that all Christians should celebrate Easter on the same day?

First Council of Nicaea Signup and view all the answers

Who was invited to the Vatican by Pope Sixtus IV to undertake a calendar reform in 1475?

Regiomontanus Signup and view all the answers

According to the Gregorian calendar, which years are leap years?

Years that are exactly divisible by 400 Signup and view all the answers

What was the main reason for establishing the Gregorian calendar?

To make the average calendar year 365.2425 days long Signup and view all the answers

What was the Julian calendar's assumption about the average solar year?

365.25 days long Signup and view all the answers

What was the effect of the Gregorian reform on the calendar year length?

The average calendar year was shortened by 0.0075 days Signup and view all the answers

What was the problem with the Julian calendar's leap year algorithm?

It had too many leap years Signup and view all the answers

What was the date when the Gregorian calendar was introduced by Pope Gregory XIII?

February 24 Signup and view all the answers

What was the problem caused by the Julian calendar's excess leap days?

The calendar drifted with respect to the equinoxes Signup and view all the answers

Which council authorised Pope Paul III to reform the calendar?

Council of Trent Signup and view all the answers

Who believed that Easter should be computed from the true motions of the Sun and Moon?

Giambattista Benedetti and Giuseppe Moleto Signup and view all the answers

What was the modification made by Aloysius Lilius to the leap year system?

Reducing the number of leap years in four centuries from 100 to 97 Signup and view all the answers

What was the long-standing obstacle to calendar reform that Aloysius Lilius solved?

The calculation of the annual date of Easter Signup and view all the answers

Who noted discrepancies in the ancient tables provided for the Sun's mean longitude?

Christopher Clavius Signup and view all the answers

What was the Gregorian leap year rule proposed by Petrus Pitatus of Verona?

97 leap years in 400 years Signup and view all the answers

What is the mean length of the Gregorian year according to the Babylonian sexagesimals?

All of the above Signup and view all the answers

What was the commonly used value for the mean tropical year in Lilius's time?

365.2425463 days Signup and view all the answers

What was the proposal made by Giambattista Benedetti and Giuseppe Moleto that was not adopted?

Computing Easter from the true motions of the Sun and Moon Signup and view all the answers

Which calendar did the Gregorian reform replace?

The Julian calendar Signup and view all the answers

What was the reason for advancing the date by 10 days during the Gregorian reform?

To correct the calculation of the date for Easter Signup and view all the answers

Which countries were the first to adopt the Gregorian calendar?

Catholic countries Signup and view all the answers

What is the difference between the Julian and Gregorian calendars?

The number of leap years Signup and view all the answers

Which country was the last European country to adopt the Gregorian calendar for civil use?

Greece Signup and view all the answers

What is the significance of the year 1582 in relation to the Gregorian reform?

The year the date was advanced by 10 days Signup and view all the answers

Do all Orthodox churches use the Julian calendar for religious rites?

No, only some Orthodox churches use the Julian calendar Signup and view all the answers