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The History Man

This blog contains interesting facts about the history of Spain and things Spanish.

Today is a LEAP DAY
Thursday, February 29, 2024 @ 9:51 AM

By The History Man

A leap year is a calendar year that contains an additional day compared to a common year. The 366th day is added to keep the calendar year synchronized with the astronomical year or seasonal year. Since astronomical events and seasons do not repeat in a whole number of days, calendars having a constant number of days each year will unavoidably drift over time with respect to the event that the year is supposed to track, such as seasons. By inserting an additional day—a leap day—into some years, the drift between a civilization's dating system and the physical properties of the Solar System can be corrected.



An astronomical year lasts slightly less than 3651/4 days. The historic Julian calendar has three common years of 365 days followed by a leap year of 366 days, by extending February to 29 days rather than the common 28.

The Gregorian calendar, the world's most widely used civil calendar, makes a further adjustment for the small error in the Julian algorithm. Each leap year has 366 days instead of 365. This extra leap day occurs in each year that is a multiple of 4 (except for years evenly divisible by 100, but not by 400).

The term leap year probably comes from the fact that a fixed date in the Gregorian calendar normally advances one day of the week from one year to the next, but the day of the week in the 12 months following the leap day (from 1 March through 28 February of the following year) will advance two days due to the extra day, thus leaping over one day in the week.

For example, Christmas Day (25 December) fell on a Friday in 2020, Saturday in 2021, Sunday in 2022, and Monday in 2023, but then will "leap" over Tuesday to fall on a Wednesday in 2024.

Leap years can present a problem in computing, known as the leap year bug, when a year is not correctly identified as a leap year or when 29 February is not handled correctly in logic that accepts or manipulates dates.


Julian Calendar

On 1 January 45 BC, by edict, Julius Caesar reformed the historic Roman calendar to make it a consistent solar calendar (rather than one which was neither strictly lunar nor strictly solar), thus removing the need for frequent intercalary months.

His rule for leap years was a simple one: add a leap day every four years. This algorithm is close to reality: a Julian year lasts 365.25 days, a mean tropical year about 365.2422 days. Consequently, even this Julian calendar drifts out of 'true' by about three days every 400 years. The Julian calendar continued in use unaltered for about 1600 years until the Catholic Church became concerned about the widening divergence between the March Equinox and 21 March.

Prior to Caesar's creation of what would be the Julian calendar, February was already the shortest month of the year for Romans. In the Roman calendar all months except February had an odd number of days – 29 or 31. This was because of a Roman superstition that 'even numbers' were unlucky. When Caesar changed the calendar to follow the solar year closely, he made all months have 30 or 31 days, leaving February unchanged except in leap years.


Gregorian Calendar

In the Gregorian calendar, the standard calendar in most of the world, almost every fourth year is a leap year. Each leap year, the month of February has 29 days instead of 28. Adding one extra day in the calendar every four years compensates for the fact that a period of 365 days is shorter than a tropical year by almost 6 hours. However, this correction is excessive and the Gregoirian reform modified the Julian calendar's scheme of leap years as follows:

Every year that is exactly divisible by four is a leap year, except for years that are exactly divisible by 100, but these centurial years are leap years if they are exactly divisible by 400. For example, the years 1700, 1800, and 1900 are not leap years, but the years 1600 and 2000 are.

Whereas the Julian calendar year incorrectly summarized Earth's tropical year as 365.25 days, the Gregorian calendar makes these exceptions to follow a calendar year of 365.2425 days. This more closely resembles a mean tropical year of 365.2422 days. Over a period of four centuries, the accumulated error of adding a leap day every four years amounts to about three extra days. The Gregorian calendar therefore omits three leap days every 400 years, which is the length of its leap cycle.

This is done by omitting 29 February in the three century years (multiples of 100) that are not multiples of 400. The years 2000 and 2400 are leap years, but not 1700, 1800, 1900, 2100, 2200 and 2300.

So, today is a Leap Day.



There is an important anomaly when it comes to salaries, wages, pay and pensions.  In effect salaried workers and wage-earners work for free today. And pensioners don't work and don't get paid for today. Since they earn a weekly wage, a monthly salary, or get paid a pension monthly, their 'remuneration' is unchanged by the extra day they have to work..

Hourly-paid workers and those in the gig economy or black economy, however, get paid for the extra day in full.




© The History Man


Acknowledgements (Photos):



India Times


Utkarsh Classes





28 February, 29 February, astronomical year, black economy, Caesar, gig economy, Gregorian calendar, intercalary months, Julian calendar, Julius Caesar, Leap Day, Leap Year, March Equinox, monthly salary, Pope Gregory, Roman calendar, salaried workers,seasonal year, Solar calendar, Solar System, tropical year, wage-earners, weekly wage

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