It is known that any given year is either an ordinary year or a leap year. Why is there such a distinction, how is time counted in each case, and how does a leap year differ from a regular year? This is discussed further.
Origin of the calendar
Periods of time called years are recorded in calendars. There you can also see the division into months, weeks and small units - days. This number system has been known since the times of Ancient Egypt. Using the calendar, people calculated when the next Nile flood would occur. It was necessary to have time to repair special structures for retaining water, so as not to be left without a crop.
The original calendar was somewhat inaccurate. It did not reflect the fact that in a year, in addition to a certain number of whole days, there are almost six more hours. Some corrections to this version of time recording were made by Julius Caesar. This type of calendar is called Julian. But the most accurate was the Gregorian calendar, which appeared even later, named after the Pope, who made adjustments to the previous version. It is by this chronology system that people in most countries now live.
Comparison
The number of whole days that make up a year, which always remains the same, is 365. And those additional six-hour segments after a certain time form another day. It is not difficult to calculate that such an additional day “grows” over four years. It is customary to add it to February - the twenty-ninth appears at the end of the month. And the year in which this happens is called a leap year.
So, the difference between a leap year and a regular year is the appearance of the 366th day. But why does February periodically become longer? This is because this month, and not December, used to be the end of the year, and it was logical to coincide one more day with the end of the next round of time. In addition, February is short, so an additional date will not be superfluous for it.
Interestingly, superstitious people have their own answer to the question of what is the difference between a leap year and a regular year. It is argued that the first of them is unsuccessful for any endeavors, such as starting a business or getting married. In addition, according to popular belief, a leap year promises unforeseen disasters and various misfortunes. However, you should not trust such signs too much. After all, this unusual year did not appear under the influence of some mystical force. It was invented by people themselves for a more accurate calculation of time.
Many people want to understand when the leap year will occur. This desire is due to the desire to realize how dangerous the upcoming not 365, but 366 days. Moreover, it is generally accepted that the coming leap year threatens with numerous dangerous events and serious disasters. Is this situation really true? Should we indulge the many experiences that are created on the basis of superstition?
Some facts from history: how did leap year appear?
The leap year appeared thanks to the formation of the Julian calendar in the distant 1st century BC. Thanks to numerous calculations, Alexandrian astrologers were able to determine the exact length of the astronomical year, which is 365 days and six hours. 
Julius Gaius Caesar, back in 445 BC, developed a calendar that he called the Julian. It should be noted that Julius Caesar is a famous emperor, dictator and commander, thanks to whom the history of the whole world has changed dramatically, including the emergence of leap years, which are even.
After it was possible to accurately determine the length of the astronomical year, it was not clear what to do with six hours, because they could not be included in the total number of days. As a result, an extraordinary decision was made: three years were to consist of 365 days. These six hours had to accumulate over four years in order for the fourth year to become a leap year and have 366 days. Moreover, the increased number of days always falls in February: 28 days (non-leap) and 29 days (leap).
Thus, the tradition regarding a leap year, which should occur every fourth year, has existed since 445 BC.
Algorithm for determining leap year.
So, in 1582, people began to follow the new Gregorian calculus, which only led to complex calculations. Now, in order to understand which year promises to be a leap year, you need to carry out serious calculations. This is due to the following nuance: scientists were calculating not the astronomical, but the solar period, which fell between the two spring equinoxes.
Scientific techniques made it possible to carry out special calculations. It turned out that every year the time shift occurs not at 6.00, but at 5 hours 48 minutes 46 seconds. Thus, a leap year must be a multiple of four, with a few exceptions. For this reason, calculations have become more difficult.
Ordinal numbers that ended in two zeros were considered non-leap numbers if they could not be divided by exactly four hundred.
Thus, two cases are assumed to allow the calculation of a leap year:
- The year number is divisible by 4, but cannot be divisible by 100.
- The sequence number can be divided by 400.
Taking into account the peculiarities of calculations, the transition of centuries ending in 00, in three cases out of four, should not be a leap year. 
What features does a leap year have?
Leap and non-leap years have important differences:
- The number of days in a leap year should be 1 more than in a regular year: 366, not 365.
- In February the 29th appears. Moreover, in non-leap years the number of days in February is 28.
- Based on popular beliefs, during a leap year, mortality, as well as the number of accidents of various types, increases.
In any case, popular beliefs say what should not be done during a leap year in order to avoid excessive risks.
What should you not do during a leap year?
- Carols should be abandoned. It is believed that people can attract increased attention from evil spirits to themselves.
- You can't talk about plans. Otherwise, your luck will run out.
- A pregnant woman should not have her hair cut, especially if she is expecting a baby during a leap year. Otherwise, the baby will be born weak.
- In a leap year, you cannot invite guests when the baby’s first tooth appears. This is demonstrated by concern for the baby’s health.
- During a leap year, you cannot sell pets or livestock. Otherwise people will face poverty.
- You can't get divorced during a leap year.
- Frequent job changes are prohibited.
- You cannot exchange housing.
- You cannot build a bathhouse.
Despite numerous prohibitions and warnings, a leap year is distinguished only by an additional day. Each person can independently decide whether to believe folk signs and how to live a leap year.
The coming year 2016, designated in the Chinese calendar as the year of the Fire Monkey, is a leap year. Since ancient times, it was believed that a leap year brings misfortune and suffering. Is this really true?
The main difference between a leap year and the rest is the number of days in the year. There are 366 of them, that is, one day more than in normal years. Where did he come from?
The tropical year does not last exactly 365 days, but 365 plus another 5 hours and 48 minutes. Over the course of four years, the extra days accumulate.
The term "leap year" first began to be used in the Roman Empire and was introduced by Julius Caesar.
In Latin it was called “bissextus”, in Greek it was pronounced “vissextus”, in Rus' - “visokos”. We added an extra day to the month of February. Later, February 29 received the name “Kasyanova Day”,
in honor of a saint who was famous for his bad character. 
By the way, in the Jewish calendar a leap year is the year
to which the month is added rather than the day. The 19-year cycle includes 12 common years and 7 leap years.
By the way, in Europe, until the 17th century, the “extra” day was considered non-existent; no transactions were concluded on this day
so that later there is no confusion in the papers, there are no problems with debt collection, etc.
February 30
From February 29th everything is clear: it is the 60th day of the leap year in the Gregorian calendar. There are 306 days left until the end of the year. But it turns out there have been cases in history when... February 30 appeared on the calendar!
February 30 is a real calendar date!
According to the Gregorian calendar, February has 28 days (in a leap year - 29 days). However, three times in February there were 30 days (two of them supposedly).
February 30, 1712 in Sweden
In 1699, the Kingdom of Sweden (which at that time included Finland) decided to switch from the Julian calendar to the Gregorian calendar. However, the Swedes did not move the calendar forward by the 11 days accumulated by that time, but decided to make the transition gradually, skipping leap years for 40 years, that is, all these years after February 28 should have gone to March 1, and every 4 years they are one day would be closer to the Gregorian calendar. Thus, 1700 was a non-leap year in Sweden.
However, despite the adopted plan, 1704 and 1708 were leap years. Because of this, for 11 years the Swedish calendar was one day ahead of the Julian calendar, but ten days behind the Gregorian calendar. In 1711, King Charles XII decided to abandon the calendar reform and return to the Julian calendar. To achieve this, two days were added in February in 1712 and thus in Sweden in 1712 it was February 30th. Sweden finally switched to the Gregorian calendar in 1753 in the usual way for all countries - the day following February 17 was declared March 1.
February 30 in 1930 and 1931 in the USSR
In 1929, it was proposed to introduce a Soviet revolutionary calendar in the USSR, where each week would have five days (five days), and each month would last 30 days or exactly six weeks. The remaining 5 or 6 days became the so-called “monthless vacation.”
Leap year myths
It just so happened that since ancient times various disasters, catastrophes, illnesses and pestilence have been attributed to the leap year. However, scientists believe that the cause of human fears is in themselves, in human psychology. After all, in nature there is no such thing as a “leap year” - people invented it. And all the popular beliefs associated with it have no scientific basis. It has long been proven that leap years are no different from ordinary years in terms of the number of natural disasters or “man-made” disasters.
Leap years have their own sad records.
For example, on February 2, 1556, a powerful earthquake occurred in China, which killed 830 thousand people. And on July 28, 1976, an earthquake in East China claimed 750 thousand lives. About 100 thousand people became victims of a powerful earthquake in Ashgabat in 1948, and in 1988, 23 thousand people died from this natural disaster in Armenia.
In 1912, the Titanic sank. Leap years also include the crash of the French airliner Concorde, the sinking of the Russian submarine Kursk, and much more.
But other natural disasters and human “creations” do not fall under the magic of leap years. A massive volcanic explosion in Indonesia in 1815 killed 92,000 people. The disastrous flood that occurred in 1887 in China on the Yellow River claimed the lives of 900 thousand people. The worst cyclone in the history of recording meteorological observations in 1970 in Bangladesh took the lives of 500 thousand people...
And many such examples can be given. The years 1905, 1914, 1917, 1941, which saw the most terrible and bloody upheavals in the history of the last century, were not leap years.
So maybe it’s not about the magic of numbers at all? The only ones who truly "suffer" are born on February 29, after all, they have to celebrate their birthday once every four years.
For those interested, read in detail about all the signs and beliefs of a leap year and debunking myths about leap years:
2016 is a leap year with 366 days instead of the usual 365. Leap year was proposed to synchronize calendars. Did you know that not every 4th year is a leap year?Why is a leap year considered unlucky, and what signs are associated with it?Here are a few facts you may not know about leap year.
What does leap year mean?
1 . A leap year is a year that has 366 days rather than the usual 365. An additional day in a leap year is added in February - February 29 (leap day).
An additional day in a leap year is necessary because a full revolution around the Sun takes a little more than 365 days, or rather 365 days, 5 hours, 48 minutes and 46 seconds.
People once followed a 355-day calendar with an additional 22-day month every two years. But in 45 BC. Julius Caesar, together with the astronomer Sosigenes, decided to simplify the situation, and the Julian 365-day calendar was developed, with an extra day every 4 years to compensate for the extra hours.
This day was added in February because it was once the last month in the Roman calendar.
2 . This system was supplemented by Pope Gregory XIII (who introduced the Gregorian calendar), who coined the term "leap year" and declared that year, multiple of 4 and multiple of 400, but not multiple of 100, is a leap year.
So, according to the Gregorian calendar, 2000 was a leap year, but 1700, 1800 and 1900 were not.
What are leap years in the 20th and 21st centuries?
1904, 1908, 1912, 1916, 1920, 1924, 1928, 1932, 1936, 1940, 1944, 1948, 1952, 1956, 1960, 1964, 1968, 1972, 1976, 1980, 1984, 1988, 1992, 1996, 2000, 2004, 2008, 2012, 2016, 2020, 2024, 2028, 2032, 2036, 2040, 2044, 2048, 2052, 2056, 2060, 2064, 2068, 2072, 2076, 2080, 2084, 2088, 2092, 2096
February 29 is leap day
3 . February 29 is considered the only day when a woman can propose marriage to a man. This tradition began in 5th century Ireland when St. Brigid complained to St. Patrick that women had to wait too long for suitors to propose.
Then he gave women one day in a leap year - the last day in the shortest month, so that the fair sex could propose to a man.
According to legend, Brigitte immediately knelt down and proposed to Patrick, but he refused, kissing her on the cheek and offering her a silk dress to soften her refusal.
4 . According to another version, this tradition appeared in Scotland, when Queen Margaret, at the age of 5, announced in 1288 that a woman could propose to any man she liked on February 29.
She also made a rule that those who refused had to pay a fine in the form of a kiss, a silk dress, a pair of gloves or money. To warn suitors in advance, the woman was required to wear trousers or a red petticoat on the day of the proposal.
In Denmark, a man who refuses a woman's marriage proposal must provide her with 12 pairs of gloves, and in Finland - fabric for a skirt.
Leap year wedding
5 . One in five couples in Greece avoid getting married on a leap year, as it is believed to brings bad luck.
In Italy it is believed that during a leap year the woman becomes unpredictable and at this time there is no need to plan important events. So, according to the Italian proverb "Anno bisesto, anno funesto". (“A leap year is a doomed year”).
Born on February 29
6 . The chances of being born on February 29th are 1 in 1461. Around the world, about 5 million people were born on Leap Day.
7 . For many centuries, astrologers believed that Children born on Leap Day have unusual talents, a unique personality and even special powers. Among the famous people born on February 29 are the poet Lord Byron, composer Gioachino Rossini, and actress Irina Kupchenko.
8. In Hong Kong, the official birthday for those born on February 29 is March 1 in normal years, while in New Zealand it is February 28. If you time it correctly, you can celebrate while traveling from one country to another longest birthday in the world.
9. The city of Anthony in Texas, USA is a self-proclaimed " world capital of leap year". A festival is held here annually, where those born on February 29 gather from all over the world.
10. Record largest number of generations born on Leap Day, belongs to the Keogh family.
Peter Anthony Keogh was born on February 29, 1940 in Ireland, his son Peter Eric was born on February 29, 1964 in the UK, and his granddaughter Bethany Wealth was born on February 29, 1996.
11. Karin Henriksen from Norway holds the world record the largest number of children born on leap day.
Her daughter Heidi was born on February 29, 1960, son Olav on February 29, 1964, and son Lief-Martin on February 29, 1968.
12. In the traditional Chinese, Jewish and ancient Indian calendars, not a leap day is added to the year, but a whole month. It is called the "intercalary month". It is believed that children born in a leap month are more difficult to raise. In addition, it is considered unlucky to start serious business during a leap year.
Leap year: signs and superstitions
Since ancient times, a leap year has always been considered difficult and bad for many undertakings. In popular belief, leap year is associated with Saint Kasyan, who was considered evil, envious, stingy, unmerciful and brought misfortune to people.
According to legend, Kasyan was a bright angel to whom God trusted all plans and intentions. But then he went over to the side of the Devil, telling him that God intended to overthrow all satanic power from heaven.
For his betrayal, God punished Kasyan by ordering him to be beaten on the forehead with a hammer for three years, and in the fourth year to be released to earth, where he committed unkind deeds.
There are many signs associated with leap year:
Firstly, on a leap year you can't start anything. This applies to important matters, business, major purchases, investments and construction.
Is it possible to get married on a leap year?
Leap year is considered extremely unsuccessful for marriage. Since ancient times, it was believed that a wedding played in a leap year would lead to an unhappy marriage, divorce, infidelity, widowhood, or the marriage itself would be short-lived.
This superstition may be due to the fact that in a leap year, girls could woo any young man they liked, who could not refuse the proposal. Often such marriages were forced, and therefore family life did not work out.
However, you should treat these signs wisely and understand that everything depends on the spouses themselves and how they build the relationship. If you do plan a wedding, there are several ways to mitigate the “consequences”:
Brides are advised to wear long dress for wedding, covering the knees to make the marriage last.
Wedding dress and other wedding accessories It is not recommended to give it to anyone.
The ring should be worn on the hand, not the glove., since wearing a ring on a glove will cause the spouses to take marriage lightly
To protect the family from troubles and misfortunes, a coin was placed in the shoes of the bride and groom.
What should you not do during a leap year?
· During a leap year don't carol at Christmas time, since it is believed that you can lose your happiness. Also, according to a sign, a caroler who dresses up as an animal or monster can take on the personality of an evil spirit.
· Pregnant women should not have their hair cut before giving birth, since the child may be born unhealthy.
· During a leap year do not start building a bathhouse, which can lead to illness.
· You can't pick mushrooms, since it is believed that they all become poisonous.
· In a leap year there is no need to celebrate the appearance baby's first tooth. According to legend, if you invite guests, your teeth will be bad.
· You can't change jobs or apartments. According to the sign, the new place will turn out to be joyless and turbulent.
· If a child is born on a leap year, it must be baptize as quickly as possible, and choose godparents among blood relatives.
· Elderly people are not allowed buy things for the funeral in advance, as this can bring death closer.
· You can't get a divorce, because in the future you will not be able to find your happiness.
sharky:
03/25/2013 at 16:04
Why on earth is 1900 not a leap year? A leap year occurs every 4 years, i.e. If it is divisible by 4, it is a leap year. And no more divisions by 100 or 400 are needed.
It’s normal to ask questions, but before you assert anything, study the hardware. The Earth revolves around the sun in 365 days 5 hours 48 minutes 46 seconds. As you can see, the remainder is not exactly 6 hours, but 11 minutes 14 seconds less. This means that by making a leap year we add extra time. Somewhere over 128 years, extra days accumulate. Therefore, every 128 years in one of the 4-year cycles, there is no need to make a leap year in order to get rid of these extra days. But to simplify things, every 100th year is not a leap year. Is the idea clear? Fine. What then should we do next, since an extra day is added every 128 years, and we cut it off every 100 years? Yes, we cut off more than we should, and this needs to be returned at some point.
If the first paragraph is clear and still interesting, then read on, but it will be more difficult.
So, in 100 years, 100/128 = 25/32 days of excess time accumulates (that’s 18 hours 45 minutes). We do not make a leap year, that is, we subtract one day: we get 25/32-32/32 = -7/32 days (that’s 5 hours 15 minutes), that is, we subtract the excess. After four cycles of 100 years (after 400 years), we will subtract an extra 4 * (-7/32) = -28/32 days (this is minus 21 hours). For the 400th year we make a leap year, that is, we add a day (24 hours): -28/32+32/32=4/32=1/8 (that’s 3 hours).
We make every 4th year a leap year, but at the same time every 100th year is not a leap year, and at the same time every 400th year is a leap year, but still every 400 years an extra 3 hours are added. After 8 cycles of 400 years, that is, after 3200 years, an extra 24 hours will accumulate, that is, one day. Then another mandatory condition is added: every 3200th year should not be a leap year. 3200 years can be rounded up to 4000, but then you will again have to play with added or trimmed days.
3200 years have not passed, so this condition, if it is made this way, is not yet talked about. But 400 years have already passed since the approval of the Gregorian calendar.
Years that are multiples of 400 are always leap years (for now), other years that are multiples of 100 are not leap years, and other years that are multiples of 4 are leap years.
The calculation I gave shows that in the current state, an error in one day will accumulate over 3200 years, but here’s what Wikipedia writes about it:
“An error of one day compared to the year of the equinoxes in the Gregorian calendar will accumulate in approximately 10,000 years (in the Julian calendar - approximately in 128 years). A frequently encountered estimate, leading to a value of the order of 3000 years, is obtained if one does not take into account that the number of days in the tropical year changes over time and, in addition, the relationship between the lengths of the seasons changes.” From the same Wikipedia, the formula for the length of a year in days with fractions paints a good picture:
365,2425=365+0,25-0,01+0,0025=265+1/4-1/100+1/400
The year 1900 was not a leap year, but 2000 was, and special, because such a leap year happens once every 400 years.
