How many days are there in a leap year?

Once every four years we observe an interesting calendar phenomenon. It is customary for us to count 365 days every year, but once every four years we count 366 days. This has happened historically, since 45 BC, when a Roman dictator named Gaius Julius Caesar created the calendar. Later, such a calendar began to be called the Julian.

The history of the leap year.

The new calendar of Gaius Julius Caesar began on January 1, 45 BC. Astronomers of that time calculated the exact number of days during which the Earth completely goes through a cycle called a year. The exact number of days was 365.25. In other words, there were 365 full days and 6 hours in a year. Since it was inconvenient to count less than a full day, we decided to introduce a special one to even out the balance.

Three years in a row are counted as 365 days, and in each subsequent fourth year 24 hours are added (6 hours in 4 years) in February. Thus, a new day of February appeared, only one, appearing every four years. This month was not chosen by chance. It was considered the last Roman month of the year. The year 45 BC became the first leap year.

The current year 2016 is a leap year. The next one will be in 2020, then in 2024, etc.

Signs of a leap year.

Since ancient times, a year in which there are one day more than in other years was considered significant and even difficult. Some events were associated with it; it was believed that if in this particular year winter is a day longer, it means that this year affects the human body in a special way.

Leap year, signs which many people are scared of, is actually not that scary. The human body is not designed for changes in the calendar and numbers. Rather, a person runs the risk of being influenced by the location of the planets, the moon and other external factors that affect the person as a whole.

Among the signs that many people have during this long year, the main ones are prohibitions on various buildings.

Leap year: what not to do?

Many of us are interested in what cannot be done in leap year . Among these activities are:

• caroling,
• make real estate transactions,
• divorce.

It is not recommended to travel far, and if this happens, it is advised to say certain prayers. All this, of course, has nothing to do with religion, so if the soul asks for prayer, it is better to pray without any signs.

Leap year is not a big deal.

A year like this can bring a person many wonderful moments. In leap years, such great figures of art and culture were born as: M. Glinka, I. Strauss, L. Tolstoy, I. Goncharov, as well as modern actors: K. Diaz, K. Khabensky, T. Hanks.

2016 is a leap year. This is not such a rare occurrence, because every 4 years the 29th day appears in February. There are many superstitions associated with this year, but is it really so dangerous? Let's try to figure this out, whether leap years are different in any way. The 21st century list regarding leap years is maintained on the same principle as before.

Leap year: definition

We all know that there are 365 days in a year, but sometimes there are 366. What does this depend on? First of all, it should be noted that we live according to the Gregorian calendar, in which those that contain 365 days are considered ordinary years, and leap years are those that are one day longer, respectively 366 days. This happens because periodically in February there are not 28, but 29 days. This happens once every four years, and this very year is usually called a leap year.

How to determine a leap year

Those years whose numbers can be divided without a remainder by the number 4 are considered to be leap years. A list of them can be found in this article. Let's say the current year is 2016, if we divide it by 4, then the result of division is a number without a remainder. Accordingly, this is a leap year. In a normal year there are 52 weeks and 1 day. Each subsequent year shifts by one day in relation to the days of the week. After a leap year, the shift occurs immediately by 2 days.

The astronomical year is counted from the first day of the vernal equinox to the beginning of the next. This period, precisely, does not have exactly 365 days, which are indicated in the calendar, but several more.

Exception

The exception is the zero years of centuries, that is, those with two zeros at the end. But if such a year number can be divided without a remainder by 400, then it is also classified as a leap year.

If we consider that the extra hours in a year are not exactly six, then the missing minutes also affect the calculation of time. It was calculated that for this reason, in 128 years, one extra day would pass in this way. In this regard, it was decided that not every fourth year should be considered a leap year, but that those years that are divisible by 100, except those that are divisible by 400, should be excluded from this rule.

The history of the leap year

To be more precise, according to the Egyptian solar calendar, introduced by Julius Caesar, the year has not exactly 365 days, but 365.25, that is, plus another quarter of a day. An extra quarter of a day in in this case is 5 hours 48 minutes and 45 seconds, which was rounded up to 6 hours, constituting a quarter of a day. But adding such a small unit of time to the year every time is impractical.

Over four years, a quarter of a day turns into a full day, which is added to the year. So February, which has fewer days than normal months, adds an extra day - and only a leap year has a February 29th.

Leap years: a list of years from the past and the 21st century. Example:

It was decided to adjust the calendar year in accordance with the astronomical one - this was done so that the seasons always occurred on the same day. Otherwise, the boundaries would shift over time.

From the Julian calendar we switched to the Gregorian calendar, which differs from the previous one in that a leap year occurs once every four years, and according to the Julian calendar - once every three years. Russian Orthodox Church and still lives according to the old style. It is 13 days behind the Gregorian calendar. Hence the celebration of dates according to the old and new styles. Thus, Catholics celebrate Christmas according to the old style - December 25, and in Russia according to the Gregorian calendar - January 7.

Where did the fear of a leap year come from?

The word "leap year" comes from the Latin phrase "bis sextus", which translates as "second sixth".

Most people associate leap year with something bad. All these superstitions go back to Ancient Rome. IN modern world days are counted from the beginning of the month, but in ancient times it was different. They were counting the days left until the beginning of the next month. Let’s say, if we say February 24, then the ancient Romans in this case used the expression “the sixth day before the beginning of March.”

When a leap year occurred, an additional day appeared between February 24 and 25. That is, in a normal year there were 5 days left until March 1, and in a leap year there were already 6, which is why the expression “second sixth” came about.

With the onset of March, the fast ended, which lasted five days, if you start from February 24, but when you add an extra day, the fast already lasted, accordingly, 1 day longer. Therefore, they considered such a year to be bad - hence the superstition about the unluckiness of leap years.

In addition, the superstition comes from the fact that only in a leap year is Kasyanov’s Day celebrated, which falls on February 29. This holiday is considered mystical. In this regard, for a long time people have been trying not to do big things in such years, not to get married, not to have children, etc. Despite the simplicity of the algorithm for determining a leap year, some may wonder: “Which years are leap years?”

Leap years of the 19th century: list

1804, 1808, 1812, 1816, 1820, 1824, 1828, 1832, 1836, 1840, 1844, 1848, 1852, 1856, 1860, 1864, 1868, 1872, 1876, 1880, 1884, 1888, 1892, 1896.

Leap years of the 20th century: their list is as follows:

1904, 1908, 1912, 1916, 1920, 1924, 1928, 1932, 1936, 1940, 1944, 1948, 1952, 1956, 1960, 1964, 1968, 1972, 1976, 1980, 1984, 1988, 1992, 1996

What years are leap years? The list of years of the current century will be constructed similarly to the previous ones. Let's take a look at it. Leap years (list) of the 21st century will be calculated in the same way. That is, 2004, 2008, 2012, 2016, 2020, etc.

Signs associated with leap year

This year, according to legend, you cannot change your usual environment. This can be understood as moving to a new place of residence, looking for a new job.

It was believed that marriages entered into this year could not bring happiness, and weddings were not recommended.

You also can’t do anything, start new things. This includes opening a business or building a house.

Let's answer the question: which years are leap years? List of 19th, 20th and 21st centuries:

It is better to postpone long trips and travel.

You can't celebrate your baby's first tooth.

Since ancient times, such years were considered dangerous, bringing many deaths, diseases, wars and crop failures. People, especially superstitious ones, fear the onset of such a year, having already prepared in advance for the worst. But are they really that dangerous?

Opinion about established superstition

The Church does not see anything bad in these years, explaining the phenomenon of a leap year as just changes in the calendar that were once made. Based on statistics, such years are no different from ordinary ones. Even if we take the issue of marriage in a leap year, which predicts a short life in marriage, then the number of divorces of “leap marriages” is no greater than among those couples who got married in ordinary years.

Hope you have a great meeting New Year, and now you are in a great holiday mood. At least that’s how it is for me - we didn’t drink any alcohol, and clinked glasses of water from a five-liter canister at midnight, so we woke up, took a walk, and then I remembered one of yesterday’s Happy New Year greetings:

I wish that at the end of each year, remembering what happened over the last 366 if ((year%4 == 0 and year%100 != 0) or (year%400 == 0)) else 365 days, think about myself:

Oh, wow, what an action that was. I will definitely tell my grandchildren or write a book about it later.

So, above is a fairly simple inline way to determine the number of days in a year (the year variable), which, in fact, fully reveals their essence: in the Gregorian calendar, leap years are considered to be those years whose serial number is either a multiple of 4, but not a multiple of 100 , or a multiple of 400. In other words, if a year is divisible by 4 without a remainder, but divisible by 100 only with a remainder, then it is a leap year, otherwise it is non-leap, except if it is divisible by 400 without a remainder, then it is still a leap year.

For example, 2013 is not a leap year, 1700, 1800 and 1900 are again not leap years, but 2000, 2004, 2008 and 2012 are leap years.

But what if we don't remember how many days there are in leap years (366 days) and non-leap years (365 days), or we just want to write the definition of the number of days in a year as quickly as possible? Is it possible to do this in Python? Of course you can.

So Python has a calendar module. It is perfect for finding out whether a year is a leap year (or, for example, how many leap years there are in a certain interval), determining the number of days in a month, getting the number of the day of the week for a certain date, and so on.

In particular, we can get the number of days in each month of the year and simply add them up.

The calendar.monthrange function takes the year number as the first argument and the month number as the second argument. Returns the number of the day of the week on the first day of the given month and the number of days in the given month:

>>> import calendar >>> calendar.monthrange(2013, 1) (1, 31)
Accordingly, we can calculate the total number of days for all 12 months, and thus obtain the number of days for a given year:

>>> import calendar >>> year = 2013 >>> sum(map(lambda x: calendar.monthrange(year, x), range(1, 13))) 365
But if you think about how exactly this line is executed, it becomes obvious that this solution is very inefficient if you need to count the number of days for large quantities years.

We check using the timeit module.

To perform it 1 million times, it takes 13.69 seconds if import calendar is done once at the beginning. If import calendar is done every time then 14.49 seconds

Now let's try another option. It requires knowing how many days there are in leap and non-leap years, but it is very short:

>>> import calendar >>> year = 2013 >>> 365+calendar.isleap(year) 365
And, as you can easily guess, it is already much faster: 0.83 seconds, including import calendar, and 0.26 seconds if import calendar is done once at the beginning.

Let's also see how long the very first option takes, with a "manual" approach: 0.07 seconds for 2012 and 2013 and 0.12 seconds for 2000 (I think everyone understands where such a difference in speed comes from for these years).

It turns out that this is the fastest option of these three:

>>> import calendar >>> year = 2013 >>> 366 if ((year%4 == 0 and year%100 != 0) or (year%400 == 0)) else 365 365
Of course, in most cases you can use any of these options - after all, when determining the number of days in one, two, ten or a hundred years, you are unlikely to notice any difference.

Write, optimize, improve, test and measure performance - but don't forget about the readability of the source code of your programs.

Happy New Year! Good luck, happiness, joy and self-improvement in the new year.

First a note. Not every 4th year is a leap year. We'll explain why later.

A normal year has 365 days. A leap year has 366 days - a day more, due to the addition of an additional day under the number 29 to the month of February, as a result of which those born on this day experience certain difficulties in celebrating their birthday.

A year is the time it takes for planet Earth to complete one revolution around the Sun in relation to the stars (apparently measured as the interval between two successive passages of the Sun through the vernal equinox).

A day (or often in everyday speech - a day) is the time during which the Earth makes one revolution around its axis. As you know, there are 24 hours in a day.

It turns out that a year does not fit exactly the number of days. There are 365 days, 5 hours, 48 ​​minutes and 45.252 seconds in a year. If a year is taken to be equal to 365 days, then it turns out that the Earth in its orbital movement will not “reach” the point at which the circle “closes”, i.e. to get to it you need to fly in orbit for another 5 hours, 48 ​​minutes and 45.252 seconds. These extra approximately 6 hours over 4 years will just be collected into one additional day, which was introduced into the calendar to eliminate the backlog, receiving every 4th year leap year- a day longer. He did this on January 1, 45 BC. e. Roman dictator Gaius Julius Caesar, and the calendar has since become known as Julian. In fairness, it must be said that Julius Caesar only introduced by authority new calendar, and it was, of course, astronomers who calculated and proposed it.

The Russian word "leap year" comes from the Latin expression "bis sextus" - "second sixth". The ancient Romans counted the days of the month remaining until the beginning of the next month. So February 24th was the sixth day until the beginning of March. In a leap year, an additional, second (bis sextus) sixth day was inserted between February 24 and February 25. Later this day began to be added to the end of the month, February 29.

So, according to Julian calendar Every 4th year is a leap year.

But it is easy to notice that 5 hours, 48 ​​minutes and 45.252 seconds are not exactly 6 hours (11 minutes 14 seconds are missing). Of these 11 minutes and 14 seconds, over 128 years, another extra day will “run up.” This was noticed from astronomical observations by the shift of the day of the vernal equinox, relative to which they are calculated church holidays, in particular Easter. By the 16th century the lag was 10 days (today it is 13 days). To eliminate it, Pope Gregory XIII carried out a calendar reform ( Gregorian calendar), according to which not every 4th year was a leap year. Years divisible by one hundred, i.e. ending with two zeros, were not leap years. The only exceptions were years divisible by 400.

So, leap years are years: 1) divisible by 4, but not by 100 (for example, 2016, 2020, 2024),

Note that the Russian Orthodox Church refused to switch to the Gregorian calendar and lives according to the old Julian calendar, which is 13 days behind the Gregorian. If the church continues to refuse to switch to the generally accepted Gregorian calendar, then in a few hundred years the shift will become such that, for example, Christmas will be celebrated in the summer.

We all know that a normal year consists of 365 days, but there is also a leap year, which includes 366 days. It occurs once every four calendar years, and the month of February in such a year includes one more day. But few people wonder why such a year is called a leap year, and today we will tell you about the origin of this name.

Origin of the name "Leap" year

As is the case with many other names known today, the origin of “Leap” Year has its origins in Latin. This year has long been called “Bis Sextus”. The Latin translation of this name means “Second Sixth”.

It is worth noting that such a calculation of time was introduced by the Romans, and in the Roman calendar BC, days were not counted in the same way as they do today. The Romans were accustomed to counting days in terms of the number of days remaining until the next month. The Romans inserted an extra day between February 23 and 24. February 24 itself was called “sectus,” which meant “the sixth day before the beginning of March.” In a leap year, when an additional day was inserted between February 23 and 24, February 24 occurred twice, which was called “bis sectus”, as we already noted - the “Second Sixth” day.

It is easy to understand that “Bis sectus” in the Slavic sense can be easily converted into “leap year”, because these names are consonant. However, in the modern Gregorian calendar, an additional day, as is known, is inserted not between February 23 and 24, but after February 28. So, once every four years, we have the opportunity to observe on wall calendars, calendars in our computers and smartphones, the day of February 29th.

Why do we need a leap year?

Having figured out why a leap year is called that, it is also necessary to take a short excursion into why such a year exists at all and why it was introduced.

We all know that a normal year consists of 365 days, we are used to it, and we do not doubt this statement for a second. However, in reality it is not entirely correct, since each year is equal to 365.4 days, that is, 365 days and 6 hours. Of course, such a calculation of time is very inconvenient, and it certainly leads to certain shifts in people’s perception of the flow of time. That is why scientific astronomers decided to calculate each multiple of four years in the amount of 366 days (using 4 excerpts of 6 hours from other years), and all the rest - 365 days exactly.