Leap years have long had a bad reputation: they are expected to bring trouble, illness, death, and even earthquakes, floods, and wars. But what is a leap year anyway, and where did it come from?
Like many things in life, leap year came to us from Ancient Rome.
From the middle of the 8th century BC, Rome used a calendar with 10 months and a year of 304 days. In the 7th century BC, the ruler Numa Pompilius reformed the calendar by adding two more months, and the year “grew” to 355 days.
However, during the reign of Julius Caesar, the Roman calendar was chaotic.
The year had 355 days, divided into 12 months, tied to the lunar cycles. However, the lunar year does not coincide with the solar year, so the Romans invented a thirteenth month of the year and named it Mercedonium - in honor of the goddess-patron of trade and payments.
Mercedonius appeared on the calendar once every two years – after February 23 in modern terms.
It could have 22 or 23 days, so the length of the year ranged from 355 to 378.
At some point, it was discovered that the calendar contained an error that led to a temporal distortion. Then the right to announce the Mercedonians was transferred to the high priest-pontiff, who was to make adjustments depending on the severity of the distortion.
However, the priest-pontiffs began to use their right for political purposes, shortening the reigns of some consuls and extending the term of office of others.
The supreme ruler of Rome, Julius Caesar, decided to rectify the situation.
When he tackled the problem, he was horrified. Because of all these changes, the Roman calendar deviated from natural realities by more than two months. And this difference was harmful primarily to agriculture, since the harvest celebration fell in mid-spring, when the harvest itself was still far away.
Caesar invited Sosigenes of Alexandria, the most respected mathematician and astronomer of the 1st century BC, to Rome.
Sosigenes proposed taking as a basis the Egyptian solar calendar, created several millennia earlier.
But before introducing the new calendar, it was necessary to eliminate the errors of the old one. All the days “lost” by the pontiffs were inserted between November and December. As a result, the year 46 BC turned out to be the longest in the entire history of mankind — it consisted of 445 days, divided into 15 months.
AUTHOR OF PHOTO, GETTY IMAGES Image caption, Agricultural events and religious festivals were closely linked in the Roman era, but they were difficult to track without a reliable calendar
From January 45 BC, Rome began to live according to a new calendar.
It was later adopted by other countries in the Western world. It received the name “Julian” calendar after the death of Julius Caesar.
Why was the year called a "leap year"?
In the Julian calendar, the extra day in leap years was not placed at the end of February, as is done now, but between the 23rd and 24th. It was called bis sextum Kalendas Martium – “twice the sixth of the Kalends of March” (the Kalends are the first day of each month). And a year with 366 days was called annus bissextus.
At the same time, Caesar moved the beginning of the year to January 1.
PHOTO AUTHOR, GETTY IMAGES Photo caption, Roman holidays and other important dates were subject to the vagaries of the calendar, which changed from year to year in unpredictable ways
Other calendar reforms
As time passed, it became increasingly obvious that an error had crept into the calculations - Roman priests were declaring a leap year not every fourth, but every third year.
The situation was corrected by Emperor Octavian Augustus.
In gratitude for this, the Roman Senate in the 8th year BC renamed the month Sextilis to Augustus (August). And the month itself received a 31st day, which was taken from the end of February. Thus, February was shortened and began to last 28 days in a common year and 29 in a leap year.
PHOTO AUTHOR, GETTY IMAGES Photo caption, Even a small difference between the calendar and the movement of the Earth around the Sun leads to discrepancies.
In 1582, Pope Gregory XIII joined the calendar reform. He created a special commission that included not only clergymen but also astronomers.
In the same year, Gregory XIII announced the creation of a new calendar, which we now know as the Gregorian calendar. It contained several significant changes. The first was that the number of days was moved forward 10 days: after October 4, the 15th came immediately. Since the Catholic Church adopted the Julian calendar only in 325 AD, a difference of 10 days accrued over 12 and a half centuries. Therefore, by the end of the 16th century, the day of the vernal equinox had “slipped” from March 21 to the 11th. Gregory XIII’s decision allowed it to be returned to March 21 as early as 1583.
As in the Julian calendar, leap years in the Gregorian calendar were years whose serial numbers were completely divisible by 4 (for example, 2024). But, in addition to this, it established a new rule: from now on, a year whose serial number was divisible by 100, but not by 400, was not considered a leap year.
For example, the years 1600 and 2000 are leap years, but 1700, 1800, 1900, and 2100 are not.
The habit of doubling February 24 in leap years, as was done in ancient Rome, gradually disappeared. Instead, a new date began to appear in calendars every four years - February 29.
The Gregorian calendar has become widespread and synchronized internationally, but unfortunately it is not perfect.
