This 2024 is a
leap year
, that is, instead of having 365 days, it has 366. One more day is added to the second month of the year and that is why we will have February 29.
The origin of leap years dates back to more than two thousand years ago.
The truth is that the most used civic calendar today, the Gregorian, is just one of many systems that humanity has devised to keep a chronology and try to synchronize the measurement of time.
There are
lunar
, lunisolar calendars - such as the one used to calculate the Chinese New Year -, religious and agricultural calendars.
Sometimes the movements of the stars are used, other times the phenomena that give way to each season: the equinoxes and the solstices.
But why do leap years exist? Did you know that they do not always occur every four years as they say?
Why do leap years exist?
Currently it is considered that a year lasts 365 days, which has been the closest estimate of the Earth's translational movement.
In other words, the time it takes our planet to complete one revolution around the sun.
However,
the measurement is not exact
.
The solar year or tropical year lasts
365 days, 5 hours and 48 minutes
.
In very simple terms, if this time difference of almost six hours were ignored, over time, a gap would occur between the calendar and the beginning of the seasons.
Therefore, when adding the almost six hours per year every four years we will have 24 hours, one extra day, which chose to be incorporated as the last day of February.
This calculation is not infallible either, measuring time was never a simple task.
However, different civilizations took up the task as a central part of their subsistence, as well as devising horoscopes and predictions.
Calculating seasonal changes also translated into a way to predict and manage the times of sowing, germination and harvest.
A Roman Emperor and a Pope: Makers of the Leap Year
In the year
46 BC.
C.
Julius Caesar
commissioned the Alexandrian astronomer Sosigenes to create a new calendar. Until then, the Roman Empire was governed by the lunar calendar based on another of Egyptian origin that consisted of 355 days.
Statue of Julius Caesar, Roman emperor who introduced the 365-day calendar.
Photo: Shutterstock illustration.
The purpose was to match solar cycles with annual weather measurements, so Sosigenes made small adjustments to the system and proposed incorporating ten days.
This is how the Julian calendar
was formed
, which had 365 days in a common year and 366 days in a leap year.
Before the new system came into effect, in 46 BC.
C. was later nicknamed “
the year of confusion
” and had 445 days to correct the errors that had accumulated with the pre-Julian calendar.
The empire adopted the new system and two additional months were added, called "July" and "August" in honor of Julius Caesar and his successor, Augustus.
Both were added between June and September, resulting in a 12-month year with an average length of 30.5 days each.
This would not be the last reform that would be made to a calendar system.
In
1582
AD.
C.
Pope Gregory XIII
promoted a second amendment that gave rise to the calendar as we know it today, under the name of the Gregorian calendar.
Pope Gregory XIII commissioned the rules of the Julian calendar to be adjusted.
Photo: Shutterstock illustration.
The supreme pontiff proclaimed a change in the measurement of days because the dates of
celebration of Easter
, agreed in the year 325 AD.
C. at the Council of Nicaea, they produced a mismatch.
Easter was to be celebrated on the Sunday after the
first full Moon after the spring equinox (in the northern hemisphere)
.
For that year, the date had moved ten days, which represented an inconvenience for calculating the rest of the festivities of the liturgical calendar.
Only in 1582
were those ten
extra days eliminated: it was dated
Friday
, October 4, and the next day, it was dated
Saturday
, October 14.
February 29 does not always occur every four years, sometimes there are exceptions.
Photo: Shutterstock illustration.
It was also decided to implement an exception to the leap year rule, which is not infallible either, but has shortened the gap between the solar year and the calendar year.
Is every four years a leap year?
Not always
In general terms, it is usually estimated that every four years there will be a leap year, but there is
an exception to the rule
.
Years that are divisible by 100 will not be leap years, unless they are also divisible by 400.
Therefore, the years 1700, 1800 and 1900 were not leap years (because they are divisible by 100), but the year 2000 was (because, in addition to being a multiple of 100, it is a multiple of 400).
For this reason, the next leap year will be 2028 and, after this, 2032. That same rule estimates, for example, it is known that the
last leap year of the 21st century
will be 2096.