No perfect calendar: Why we have leap years – DW – 02/28/2020 (2024)
Family lore has it my father was born on February 29, 1936 - a leap day in a leap year many moons ago. It seems fitting for a man who says he's "not interested" in birthdays that he should have the option of missing his three years out of (almost) every four.
But given my dad's talent for spinning yarns (he started his working life in markets), it's possible he wasn't even born in 1936, but in 1935, and that was just a bog-standard, "common" year.
Hold on: what's the difference between a common year and a leap year?
In the Gregorian calendar, one of the most widely used calendars in the world, a common year is your standard "365-day" cycle. A leap year, however, has 366 days. It's an attempt at improving the accuracy of the Western-Christian calendar to keep it in sync with the Earth's rotations around the sun and "fixed" astronomical events, such as the equinoxes and solstices.
Put simply: there's no perfect calendar. A calendar depicts a year, usually an imperfect year.
A year is the time it takes for the Earth to orbit the sun. We say it takes 365 days for the Earth to orbit the sun - but that's not strictly true. A true year - known as a tropical year, solar year, astronomical year or equinoctial year - is the time it takes the sun to pass from vernal (or spring) equinox to vernal equinox. That's 365 days, 5 hours, 48 minutes, and 46 seconds, or 365.2422 days to be precise. So there's roughly a six-hour margin of error in every "common year." Leap years compensate for the extra 0.2422 of a day. Failing to compensate for these "extra" hours would send us out of sync with the seasons - by about 24 days after only 100 years.
A common year is 365 days, which is about a quarter of a day shorter than a tropical year. At 366 days, leap years are three-quarters of a day longer than a tropical year. Over time, the combination of common and leap years keeps us roughly in sync with the Earth's orbit of the sun.
How often do we have leap years?
Leap years occur almost every four years, with some exceptions.
What's this about "almost" every four years?
Leap years were introduced by that grand old Roman, Julius Caesar, in the Julian calendar. Back then, leap years occurred every four years without fail. But it was felt this over-compensated. The Gregorian calendar was then devised by Aloysius Lilius, an Italian astronomer and philosopher, (and named after Pope Gregory XIII) to replace the Julian calendar, with stricter criteria for leap years.
In the Gregorian calendar, leap years are those that can be evenly divided by four — unlessthey can also be divided by 100, in which case they are nota leap year.
However —and this is an exception to the rule that came into effect in the year 2000 — if ayear can be divided by 4 (leap year), 100 (not a leap year), but also 400, then it canbe considered a leap year.
We have to skip some leap years to account for the fact that those extra, or decimal hours (the 5 hours, 48 minutes, and 46 seconds) in the tropical year are just short of a quarter day. So in a sense we're re-adjusting the re-adjustment, but we're still left with an imperfect sum.
Battle of the calendars
The Gregorian calendar was first adopted in Italy, Poland, Portugal and Spain in 1582. It is regarded as one of the most accurate calendars in use today. But it maintains a margin of error of about 27 seconds per year - that's one day in every 3236 years. It's fourth in line for accuracy behind the Mayan calendar from about 2000 B.C.E. (margin of error: one day in every 6500 years), the Revised Julian Calendar from 1923 (margin of error: one day in every 31,250 years), and the Iranian Solar Hijri calendar from the 2nd millennium B.C.E. (margin of error: one day in 110,000 years). The Solar Hijri is said to achieve its high accuracy by using astronomical observations rather than mathematical ones.
Do other calendars have leap years?
Yes. The Chinese calendar has leap years featuring leap months - rather than leap days as in the Gregorian. A Hindu leap year also features an extra month. The Ethiopian calendar has 13 months, where the 13th month has five days in a common year and six in a leap year. The Islamic leap year occurs 11 times in a 30-year cycle. And a Jewish leap year has between 383 and 385 days, occurring seven times in a 19-year cycle.
And does all this leaping do us any good?
We do a fair bit of leaping about - even adjusting Universal Time with leap seconds to account for irregular changes in the Earth's rotation. It can be very important for people to feel they are in sync with time and astronomical events, for instance, for religious reasons, such as Easter, which is tied to the Spring Equinox. But if not for religious or, say, environmental reasons, does it really matter if the seasons drift from month to month, or if we lose hours and days over thousands of years? Would we even notice?
The earth takes 36514 days Le one year to complete one revolution around the sun. We consider a year as consisting of 365 days only and ignore six hours for our convenience. Six hours saved every year are added to make one day Le 24 hours over a span of four years. This surplus day is added to the month of February.
The short explanation for why we need leap years is that our calendar needs to stay aligned with the astronomical seasons. One orbit of Earth around the Sun takes approximately 365.25 days—a little more than our Gregorian calendar's nice, round number of 365.
Our planet takes approximately 365.25 days to orbit the sun once. It's that . 25 that creates the need for a leap year every four years. During non-leap years, aka common years – like 2022 – the calendar doesn't take into account the extra quarter of a day required by Earth to complete a single orbit.
Nearly every four years, we add an extra day to the calendar in the form of February 29, also known as Leap Day. Put simply, these additional 24 hours are built into the calendar to ensure that it stays in line with the Earth's movement around the Sun.
To fix his culture's calendar, Roman emperor Julius Caesar created the Year of Confusion when he decided that the year 46 B.C. was going to be 445 days long instead of 365 days long. He then made a 365.25-day year—a tiny bit longer than the 365.2422 solar year—that added a leap day every fourth year.
And why is it called “leap year?” Well, a common year is 52 weeks and 1 day long. That means that if your birthday were to occur on a Monday one year, the next year it should occur on a Tuesday. However, the addition of an extra day during a leap year means that your birthday now “leaps” over a day.
It is the 60th day of a leap year in the Gregorian calendar, and 306 days remain until the end of the leap year. It is also the last day of February on leap years. It is also the last day of meteorological winter in Northern Hemisphere and the last day of meteorological summer in the Southern Hemisphere on leap years.
The bad news, this year is not a leap year since it is only 2022, but the good news is the next leap year is 2024, only 2 years or about 730 and a half days away! From that point, the following leap years would be 2028, 2032 and 2036.
Earth is estimated to be 4.54 billion years old, plus or minus about 50 million years. Scientists have scoured the Earth searching for the oldest rocks to radiometrically date. In northwestern Canada, they discovered rocks about 4.03 billion years old.
Those born on that day don't always get to celebrate their actual birthday — since that date occurs only every four years. Someone born on Leap Day typically celebrates birthdays on Feb.28 or March 1 and uses one of those dates for identification and important documents.
In general terms the algorithm for calculating a leap year is as follows... A year will be a leap year if it is divisible by 4 but not by 100. If a year is divisible by 4 and by 100, it is not a leap year unless it is also divisible by 400.
The Julian Calendar added a little more than 10 days to each year, making each month either 30 or 31 days long, except for February. To account for the entire 365.25 day-long year, one day was added to February every four years, now known as a “leap year.” During most years, this left February with just 28 days.
In 46 BCE the Julian calendar introduced a leap day every four years, but a problem with the measurement that was used led to a mounting discrepancy over the course of several centuries. The Gregorian calendar reformed the concept in 1582 by eliminating leap years in century years that weren't exactly divisible by 400.
By 1582 A.D. that slight discrepancy in the Julian calendar added up to 10 days. So Pope Gregory XIII created the Gregorian calendar, coined the term “leap year” and established February 29 as the official date to add to a leap year.
In non-leap years, that day is March 1. So for someone born on February 29, the first day they can legally drive, vote, join the Army, buy alcohol or start collecting Social Security is presumably March 1 in non-leap years.
Life coach and author Tony Robbins was born on Leap Day in 1960. He's celebrating his 60th birthday. Carlos Humberto Romero, former president of El Salvador, was born on Leap Day in 1924. Al Rosen, former third baseman for the Cleveland Indians, was also born on Leap Day in 1924.
The tradition of Leap Year began more than 2,000 years ago to "leap" the 365-day calendar year ahead one day almost every four years to keep up with the solar year, which is actually 365.2425 days long. Roman Emperor Julius Caesar is considered the father of Leap Year, according to the History Channel.
February 30. February 30 or 30 February is a date that does not occur on the Gregorian calendar, where the month of February contains only 28 days, or 29 days in a leap year. February 30 is usually used as a sarcastic date for referring to something that will never happen or will never be done.
The Sumerians in Mesopotamia made the very first calendar, which divided a year into 12 lunar months, each consisting of 29 or 30 days. The Sumerian calendar was very different from the one we use today. Here's how: One year had 360 days.
The Roman ruler Numa Pompilius is credited with adding January at the beginning and February at the end of the calendar to create the 12-month year. In 452 B.C.E., February was moved between January and March. By the 1st century B.C.E., the Roman calendar had become hopelessly confused.
Because such years are rarer than normal years, they have become lucky omens. Indeed the 29th February itself is an especially important day. Anything started on this day is sure of success. Certainly February 29th in the leap year of 1504 was very successful for one Christopher Columbus.
People born on leap day are often called "leaplings" or "leapers." Most of them don't wait every four years to celebrate their birthdays, but instead blow out the candles on Feb. 28 or March 1. According to History.com, about 4.1 million people around the world have been born on Feb.
Also, in 100 years there are 24 leap years. A year in which is divisible by 4 and for century years it should be divisible by 400 not 100 then it is said to be leap year. For example 100 is not leap year even though it is divisible by 4 but as it is century year it should be divisible by 400.
The date of birth of Jesus is not stated in the gospels or in any historical sources but most biblical scholars assume a year of birth between 6 and 4 BC.
Adam is the name given in Genesis 1-5 to the first human. Beyond its use as the name of the first man, adam is also used in the Bible as a pronoun, individually as "a human" and in a collective sense as "mankind".
What is the rarest birthday? The least common birthday is leap day, or February 29. But because the day only occurs once every four years, it's obvious it would yield the least amount of birthdays. The rarest birthday of the 365 annual calendar days is Christmas day, Dec. 25.
February 3rd is the only day where no one in history has ever been born. Despite much scientific study, there is no explanation for this phenomena. Historically it has been referred to as “the empty day” or “nobody's birthday”.
Experian landed on September 9 as the most common birthday in the U.S. It's shared by comedian Adam Sandler, actor Hugh Grant, jazz singer Michael Bublé, Russian literary giant Leo Tolstoy, and Colonel Sanders, the founder of KFC.
If a year is divisible by 100, but not 400, then it is not a leap year. If a year is divisible by both 100 and 400, then it is a leap year. For example, 1900 is evenly divisible by 100, but not 400 since it gives you a result of 4.75. This means that 1900 is not a leap year.
It is regarded as one of the most accurate calendars in use today. But it maintains a margin of error of about 27 seconds per year - that's one day in every 3236 years.
A leap year is a year containing an extra day. It has 366 days instead of the normal 365 days. The extra day is added in February, which has 29 days instead of the normal 28 days. Leap years occur every 4 years.
NOTE: When a century year leaves a remainder 0 when divided by 400 then it is a leap year (366 days). So, only 1200 is completely divisible by 400 so 1200 is a leap century year. So, there are 366 days in the 1200 year. So, 1200 has 366 days.
Introduction: My name is Duane Harber, I am a modern, clever, handsome, fair, agreeable, inexpensive, beautiful person who loves writing and wants to share my knowledge and understanding with you.
We notice you're using an ad blocker
Without advertising income, we can't keep making this site awesome for you.
