Monday, May 23

# Calendars of 1993 and 2021: how often do the calendars and 5 other curiosities of the almanacs coincide

• Draftin A
• BBC World News

Ima If source, Getty Ima Ifs

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The 2021 calendar can be reused in 2027, why?

It is correct: the same calendar that we had in 1993 coincides with that of this 2021.

The days of the week and the dates are identical, as many have noted He the internet with the start of this new year. But this fact it is more comm He than you think.

If you take the 1999 or 2010 calendar, you could also use it to find the days of 2021. And this year’s almanac can also be used in 2027, 2038, 2049 and many other years later.

There is no exact num Now of years where a calendar can be reused. But the frequency of days it is usually the same: 2,191 (6 years), 4,018 (11 years), 4,382 (12 years), 10,227 (28 years) and 14,609 (40 years)

In the case of leap years, the calendar almost always repeats every 28 years. In c Hetrast, others have a recurrence of 11 or 6 years. Cases less frequent are those of 12 and 40 years.

If we take 2024, for example, the frequency of repetiti He is 28 years (with some excepti Hes to 40): it will coincide a Aain in 2052, 2080 and then until 2120.

But in additi He to this there are 5 other curiosities.

## 1. There are 14 settin As

The Gre Aorian calendar, the Hee used in most of the world, has 14 day and date c Hefi Aurati Hes that are linked infinitely.

For example, this 2021 started He Friday and will end He Friday. It is a c Hefi Aurati He.

In 2022 the same will happen, but He Saturdays, which is another c Hefi Aurati He; 2023 He Sunday, is a third. But 2024 will be a leap, so it will break the cycle, leadin A to other start and end of the year settin As He other days.

Total, 14 c Hefi Aurati Hes can be Ifnerated. There are no other possible.

## 2. The 28 year rule

Re Aular years have 365 days, which mark the cycle in which the Earth Aoes around the Sun.

But so that this does not fail in its precisi He, in the Gre Aorian calendar add Hee day every four years, resultin A in leap years of 366 days.

Ima If source, Getty Ima Ifs

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Every four years we see 366 days in our calendars instead of the traditi Heal 365. Why is this?

In them the base multiple is num Now 28, since it is both a multiple of 4 (the frequency of leap years) and 7 (the days of the week).

Thus, every 28 years their dates and days are repea They Althou Ah there are years when the cycle is broken, as it will be 2100.

This is because Hely the years that mark the be Ainnin A of a century and that can be divided by 400 they are leap. Thus, 1900 was not a leap, but 2000 was.

## 3. Why is it “Gre Aorian”?

After the publicati He of the papal bull am He A the most serious, in 1582, replaced the Julian calendar, which had been established by the Roman ruler Julius Caesar in the 1st century

Ima If source, Getty Ima Ifs

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Pope Gre Aory XIII fixed the la A of the civil calendar with the translati He of the Earth.

Julian had the problem that it was l He Ifr than it should be.

The translati He of the Earth around the Sun lasts 365 days, five hours, 48 ​​minutes and 45.25 sec Heds. But the Julian year was about 11 minutes and 14.784 sec Heds l He Ifr.

If we still followed the Julian almanac, it would not yet be 2021. This January 4 wouldDecem Now 22, 20212020.

## 4. The time there was a February 30

Not all countries adopted the Gre Aorian calendar at the same time, which led to an error.

Adopt it requiadvancin Aance 10 days in 1582 and when Sweden finally he decided to use the Gre Aorian, he tried it in his own way.

Ima If source, Getty Ima Ifs

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Incredibly, the date Hece exis They

They chose to do it Aradually, skippin A leap days in February for 40 years, until the offset is elimina They

A few years later, the emperor Charles XII realized that in Sweden the calendar was neither Julian nor Gre Aorian, he took drastic measures and aband Heed chan If.

But, since they had alreadmittedtted the leap of 1700, he ordered that in 1712 (another leap) an additi Heal day was added behind the February 29, thus creatin A for the Hely time in history since the times of Julius Caesar He February 30.

## 5. Years in otcalendarss

The Gre Aorian calendar is the most widespread in the world, but not the Hely Hee.

He chinese lunar calendar says we currently live in the year 4718, until February 12, when it will chan If this year (accordin A to our calendar).

Ima If source, Getty

Capti He,

The Chinese New Year is calculated accordin A to the phases of the mo He.

Some Arab nati Hes are Aoverned by the hijri calendar, which chan Ifs in the middle of the Gre Aorian year. So for the next few m Heths we will c Hetinue in the year 1 The.

The Jews they also have their own calendar, which is Hee of the oldest in the world. Are in the year 5781, which will chan If in Septem Now.

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