What Is a Leap Year?

Learn How Leap Years Keep Our Calendar Accurate

December 30, 2020
29 Leap Year Fence

Leap years keep our calendars in check! Allow us to explain why leap years are necessary and share some of the fun folklore surrounding them. 

What Is a Leap Year?

Simply put, a leap year is a year with an extra day—February 29—which is added nearly every four years to the calendar year.

Why Are Leap Years Necessary?

Adding an extra day every four years keeps our calendar aligned correctly with the astronomical seasons, since a year according to the Gregorian calendar (365 days) and a year according to Earth’s orbit around the Sun (approximately 365.25 days) are not the exact same length of time. Without this extra day, our calendar and the seasons would gradually get out of sync. (Keep reading for a longer explanation.) 

Because of this extra day, a leap year has 366 days instead of 365. Additionally, a leap year does not end and begin on the same day of the week, as a non–leap year does.

How Do You Know If It’s a Leap Year?

Generally, a leap year happens every four years, which, thankfully, is a fairly simple pattern to remember. However, there is a little more to it than that.

Here are the rules of leap years:

  1. A year may be a leap year if it is evenly divisible by 4.
  2. Years that are divisible by 100 (century years such as 1900 or 2000) cannot be leap years unless they are also divisible by 400. (For this reason, the years 1700, 1800, and 1900 were not leap years, but the years 1600 and 2000 were.)

If a year satisfies both the rules above, then it is a leap year. 

When Is the Next Leap Year?

Leap Year Leap Day
2024 Thursday, February 29
2028 Tuesday, February 29
2032 Sunday, February 29
2036 Friday, February 29

Why Do We Need Leap Years?

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. Because the calendar does not account for the extra quarter of a day that the Earth requires to complete its orbit around the Sun, it doesn’t completely align with the solar year. 

Because of this .25 difference, our calendar gradually gets out of sync with the seasons. Adding an extra day, aka a “leap day,” to the calendar every 4 years brings the calendar in line and therefore realigns it with the seasons.

Without leap days, the calendar would be off by 5 hours, 48 minutes, and 45 seconds more each year.

After 100 years, the seasons would be off by 25 days! Eventually, the months we call February and March would feel like summer months in the Northern Hemisphere.

The extra leap day adjusts this drift, but it’s not a perfect match: Adding a leap day every four years overcompensates by a few extra seconds each leap year, adding up to about three extra days every 10,000 years. 

What Is a Leap Day? And a Leapling?

A “leap day” is the extra day in the leap year: February 29.

A “leapling” is a person born on a leap day. Any leap day babies out there? We’d love to hear from you in the comments below!

Leap Year Facts and Folklore

  • Ages ago, Leap Day was known as “Ladies Day” or “Ladies’ Privilege,” as it was the one day when women were free to propose to men. Today, Sadie Hawkins Day sometimes applies to Feb 29 (leap day), based on this older tradition.
  • According to folklore, in a leap year, the weather always changes on Friday.
  • “Leap year was ne’er a good sheep year” (old proverb)

Are Leap Years Bad Luck?

Many feel that to be born on Leap Day, thereby becoming a “leapling,” is a sign of good luck.

In some cultures, it is considered bad luck to get married during a leap year.

We don’t know of any evidence supporting that marriage theory, but we do know that during leap years:

  • Rome burned (64),
  • and the Titanic sank (1912).

By the same token, also in leap years:

  • the Pilgrims landed at Plymouth, Massachusetts (1620),
  • Benjamin Franklin proved that lightning is electricity (1752),
  • and gold was discovered in California (1848).

Do you have any leap year memories? Are you a Leapling yourself? Please share in the comments below!


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When was the first leap year?

When was the first leap year?

Methods to synchronize

The Editors's picture

Methods to synchronize various calendars with astronomical events have been used for thousands of years. But for the present-day leap year rule for the Gregorian calendar, it started for Britain and its colonies (including America) back in 1752, when the country switched from the Julian calendar to the Gregorian. Other countries that had used the Julian calendar made the switch earlier, some as far back as 1582, when the Gregorian calendar had first been introduced. (It was named for Pope Gregory XIII, who was involved in reforming the Julian calendar).
It is interesting to note that in the American colonies prior to 1752, New Year's Day for civil purposes was celebrated on March 25 (Lady Day, or Annunciation). So, for example, March 24, 1701, would be followed by March 25, 1702. February was the twelfth month of the year.

An Act of Parliament in 1751 in Great Britain (which applied to the American colonies as well) adopted the Gregorian calendar effective 1752, and also proclaimed January 1 as the beginning of the calendar year (thereby making February the second month). This meant that 1751 was a short year, starting March 25 and ending December 31--there were no January and February in 1751 for Britain and its colonies (but this wasn't the case in other countries already using the Gregorian calendar). January 1, 1752, started the new year, which ended on December 31, 1752.

The Act also stated that, in order to catch up to the actual time (the Julian calendar that they had been using was 11 days ahead at the time to Earth's actual orbit), September 2, 1752, would be followed by September 14, 1752. (Eleven days were dropped for that year.)
Starting in 1752, the leap year rules for the Gregorian calendar applied to Britain and its colonies. For those countries that had adopted the Gregorian calendar earlier, the first leap year in the modern sense also occurred earlier.
The Julian calendar also has leap years, but it follows a different set of rules, adding a leap day every four years.

To be honest nobody knows for

To be honest nobody knows for sure when the first leap year was although there is a theory that it was in 1752. Hope this answered your question GOODBYE

Leap year


Leap year

It was 2000

Year 4 XD

Year 4 XD

Leap Years

On the 4th year god said let there be leap

I have a related question

I have a related question about the 400 rule. I recently (last night) got in to a bit of a discussion about leap years and said that only those centuries which are divisible by 400 are leap years (Leap Centuries) but those not divisible are not leap years. But I added: That year zero (Year X(ex) was not a leap year because zero is not divisible by 400. I was immediately asked what I meant by year zero (X). I said, I meant “the year when Christ (Χριστός) was born”. The year preceding 1 AD. I knew when asking that some of my friends have said that year zero doesn't exist. So that was partly why I had been considering it. Then yesterday I was discussing when leap years occur and how some are and some aren't according to the 400 year rule. So the years 2400AD, 2000AD, 1600AD, 1200AD, 800AD, 400AD will be or were leap years and 400BC and 800BC would have been if the rule existed during those times. Logically year Zero between 400AD and 400BC would follow that general mathematical sequence and so at first I thought that therefore obviously the year of the birth of Christ (Χριστός) would have been a leap year. (I also was aware some people say he was born 2BC, but that did not come in to it, because it was a question of mathematics, Leap years and the leap year rule (hypothetical, if he had been)). So I was at first happy to believe the year of his birth (Year zero) was in deed a leap year. About thirty minutes later I was applying the 400 rule when suddenly I realised that zero (naught) is not divisible by 400. So there fore it is an exception to the 400 rule. So 12BC, 8BC, 4BC, 4AD, 8AD and 12AD were leap years but year Zero was not as Zero was not divisible by 400. But then my friend (Amazing mathematical Abilities (Teaches mathematics) said that Zero was divisible by 400. He briefly and swiftly explained an example ( something about vectors) an explanation which was too brief and swift for me who by then was experiencing difficulties with what he had just said. So he seemed to contradict my basic understanding that nothing divided by anything is nothing.
I respect his abilities at maths as I know they are far greater than mine in many ways. But I was still interested to know if I was wrong or my basic education was wrong and so therefore fore he was right. I started a bit of research and found some sites would side with 0/x=0 where as some of the other more advanced sites seemed to make different statements about various branches of mathematics which all seemed above my abilities as I have not the time for an in-depth study of those higher aspects. I became more focused on the concept of 0/x=0 or undefined, pertaining to the impossibility of the concept and so mathematicians had left it undefined as a suitable definition. That seemed to suit my purpose of the mathematics. It left me still with the basic concept that zero divided by any number equals zero. So my friend could also be right as it is right for some maths and for other maths 0/x=0 is considered correct. But he was really saying that for the purpose of leap years, “year-zero” would be a leap year contrary to my mathematical belief that zero is not divisible by 400.
So I am still uncertain which way to decide. So I decided to ask others for their views. I realise some may say there is no year zero so the question is unrealistic. I would accept that as a realistic and valid answer as I am also yet undecided if there was a year zero or not for the purpose of some calculations. But for other situations I am sure there is a year zero. Or there is a year before the birth of Christ. (Well maybe there is, (Just depends how far a person wants to go or something).
So that is the question pertaining to leap years and the rule of dividing by 400. Is year zero (which I call year “X” some times) divisible by 400? Was that millennial year a leap year like the year 2000AD and 2000BC (but not 1000AD or 1000BC)? So sequentially leap years were: -20BC, -16BC, -12BC, -8BC, -4BC, 0?, +4AD, +8BAD, +12AC. +16AD, +20AD...ETC. ETC.? (AD could be replaced by CE (Christian Era or Common Era))? Thank you.

There was no year 0. The

There was no year 0. The year before 1 was year -1.

Zero divided by a number.


By definition: divisible means an integer is capable of being divided by another integer without a fractional remainder.

or you can think of it as being able to divide a number into equal "whole" parts with no remainder.

The number "zero" can be divided by "any number" into equal parts of "zero". The only exclusion is you cannot divide zero by itself. That is undefined.

So the answer to "zero" divided by 400 is "zero" with no remainder and therefore "zero" is divisible by 400.


I apologize in advance for

I apologize in advance for any ambiguity.

"With this rule, 97 leap days are added every 400 years, which means the average length of year in the Gregorian calendar is 365.2425 days."

If the rule off 400 is applied to centuries, would that not leave 96 leap years in a 400 year period instead of 97?

e.g. 100/4 = 25

However, since 100 isn't divisible by 400 creating a whole number, wouldn't we say 24 leap days happen over a 100 year span?

e.g. 24 x 4 Centuries = 96 Leap Days over a 400 year period?

I think I see where you have

I think I see where you have miss calculated.
So if we use the divisible by 400 rule we have one century in 4 being a leap year where as the other three are not. So the year 1600 would have been a leap year and 1700, 1800, and 1900 were not.
So there are 25 leap years in every century which starts with a leap year (EG 1600, 2000, 2400)and only 24 leap years in the century's which are not divisible by 400. So 3 times 24 + (1 Times 25) equals 97. I think you just forgot to add the leap year for the century beginning with a leap year. so you went for, “times 25” instead of “3 times 25 plus 1 times 24”.

In twenty centuries such as between the years 2000 and 4000 there would be only 5 Centuries which begin on a Leap year.

Hold on what u mean by

Hold on what u mean by something divisible by 400?

My cousin is 15 but really

My cousin is 15 but really 3years old

Hi, who came up with the idea

Hi, who came up with the idea of Leap Year, and that it should be in February and no other month like July? I understand that there are different days in each months are, 31, 28/29, 31, 30, 31, 30, 31, 31, 30, 31, 30, 31 days/month. Instead of a leap year, the days in August could be 31, then the series goes on......

Leap years do not occur every

The Editors's picture

Leap years do not occur every year; this is why we can't just add an extra day to a month. The cycle of the seasons (or, a tropical year) is approximately 365.2422 days. Since a calendar year consists of an integral number of whole days, a calendar year cannot exactly match the tropical year. To align the current calendar with the seasons (and how the Earth orbits around the Sun), leap year rules were created. No system is perfect but that is the background.

Well if this was in maybe

Well if this was in maybe let's say December then winter has 1 more day then should because winter is for however long Sumer fall and spring same so I'd winter gets it and somewhere else does then winter will be in next season time but feb is in spring and spring prob has that about .25 of the day so every 4 years that 1 day takes out the .25 for spring but if it's in fall then fall is to long and spring is to shor

August has have 31 days for

August has have 31 days for many many leap and common years

John was born on Feb

John was born on Feb 29happened to be a Wednesday. If he lives tobe 101 years old, how many birthdays would he celebrate on a Wednesday?

Three (3). If he was born on

Three (3).

If he was born on Wednesday 29th February 2012 and assuming he does not celebrate his 1st birth year because he is just popping out of the womb then he would reach age 28 in the year 2049 when his next birthday falls on a leap Wednesday. (Wednesday 29 February 2040). Then at age 56 he could celebrate his second leap Wednesday in 2068. The last one would be at age 84 in the year 2096. The next one after 101 years would be 2108 and John would have to be 112 years of age.
The answer is still 3 if he was born on either Wednesday 29th February 1888
Wednesday 29th February 1928
Wednesday 29th February 1956
Wednesday 29th February 1984.

A Complete List of Leap Wednesdays from the year 1500 AD to the year 2508 including the number of year difference.

Wednesday 29 February 1520 0
Wednesday 29 February 1548 28
Wednesday 29 February 1576 28
Wednesday 29 February 1584 8
Wednesday 29 February 1612 28
Wednesday 29 February 1640 28
Wednesday 29 February 1668 28
Wednesday 29 February 1696 28
Wednesday 29 February 1708 12
Wednesday 29 February 1736 28
Wednesday 29 February 1764 28
Wednesday 29 February 1792 28
Wednesday 29 February 1804 12
Wednesday 29 February 1832 28
Wednesday 29 February 1860 28
Wednesday 29 February 1888 28
Wednesday 29 February 1928 40
Wednesday 29 February 1956 28
Wednesday 29 February 1984 28
Wednesday 29 February 2012 28
Wednesday 29 February 2040 28
Wednesday 29 February 2068 28
Wednesday 29 February 2096 28
Wednesday 29 February 2108 12
Wednesday 29 February 2136 28
Wednesday 29 February 2164 28
Wednesday 29 February 2192 28
Wednesday 29 February 2204 12
Wednesday 29 February 2232 28
Wednesday 29 February 2260 28
Wednesday 29 February 2288 28
Wednesday 29 February 2328 40
Wednesday 29 February 2356 28
Wednesday 29 February 2384 28
Wednesday 29 February 2412 28
Wednesday 29 February 2440 28
Wednesday 29 February 2468 28
Wednesday 29 February 2496 28
Wednesday 29 February 2508 12

And they said there were no

And they said there were no dumb questions.

My husband and I's

My husband and I's anniversary is Feb 29th. So far we have gotten to celebrate it on the actual date 2 times almost 3 ;) When we don't have a leap year we celebrate the day before and the day after. This year is our 10 year mark and I love him more and more each day!!

I heard an old saying that

I heard an old saying that being born on Feb. 29 means you will live longer. Is their any truth behind this?

We aren't aware of studies on

The Editors's picture

We aren't aware of studies on this. It could be that the saying may have come about because if one only counts a person's age as the number of official birthday dates that s/he passes over the years, then a person born on leap day will not have as many birthdays as others, and therefore will be "younger" and have a longer time to reach old age. For example, someone 100 years old in normal reckoning, might be only have lived through 24 or so leap days, so might also be considered as being in his/her 20s.

If you were shot at age 10 or

If you were shot at age 10 or kill by stepping in to a moving bus at age 11 then you would not have lived longer than those who lived longer. It all depends on when you die. I believe there is absolutely no truth in the saying at all. With births occuring on a leap day being only 0.00273% (mean statistics) of total births a year and therefor only (68 ten-thousanths)per 4 year cycle then it sems likey that that tiny minority would not live longer than the far greater majority. In other words there is 1 leap day per 1,461 days. So it seems unlikely that those born on that single day will out live those born on either of the 1,461 days. But that doesn't mean that a person born on that leap day is going to live a shorter life. He has as much chance. So the statistics are just a mean calculation indicating a general rule for general data and not an indication that a person will or will not live as long. I believe that it is not possible to actually calculate the actual reality as the closest a person could calculate would be a proportional calulations. Such as no. or births over 100 years on the 29 and all the other days and number of deaths divided by the proportions 1:1461. That would only give a proportional representation. Then try to calculate in the consequenses of wars and you have an impossible calculation. Even if you could calculate it the numbers would still not garantee either group would live longer as those numbers could change at any time dependant upon circumstances. So it seems to me that the only sensible conclusion is that there is no evidence that indicates either group WILL or DOES live longer.

There is no evidence that

There is no evidence that people live longer if they were born on Feb. 29. No one knows when someone might die (unless they threaten you to kill you on a sirten day)

Hi there - How many weeks are

Hi there - How many weeks are there till the next leap year in 2016?

There are 76 Mondays to go

There are 76 Mondays to go till the next leap Monday in 2016 from to day 21st September 2014 and 75 from tomorrow Monday 22nd 201.

1 Monday 22 September 2014 75

2 Monday 29 September 2014 74

3 Monday 6 October 2014 73

4 Monday 13 October 2014 72

5 Monday 20 October 2014 71

6 Monday 27 October 2014 70

7 Monday 3 November 2014 69

8 Monday 10 November 2014 68

9 Monday 17 November 2014 67

10 Monday 24 November 2014 66

11 Monday 1 December 2014 65

12 Monday 8 December 2014 64

13 Monday 15 December 2014 63

14 Monday 22 December 2014 62

15 Monday 29 December 2014 61

16 Monday 5 January 2015 60

17 Monday 12 January 2015 59

18 Monday 19 January 2015 58

19 Monday 26 January 2015 57

20 Monday 2 February 2015 56

21 Monday 9 February 2015 55

22 Monday 16 February 2015 54

23 Monday 23 February 2015 53

24 Monday 2 March 2015 52

25 Monday 9 March 2015 51

26 Monday 16 March 2015 50

27 Monday 23 March 2015 49

28 Monday 30 March 2015 48

29 Monday 6 April 2015 47

30 Monday 13 April 2015 46

31 Monday 20 April 2015 45

32 Monday 27 April 2015 44

33 Monday 4 May 2015 43

34 Monday 11 May 2015 42

35 Monday 18 May 2015 41

36 Monday 25 May 2015 40

37 Monday 1 June 2015 39

38 Monday 8 June 2015 38

39 Monday 15 June 2015 37

40 Monday 22 June 2015 36

41 Monday 29 June 2015 35

42 Monday 6 July 2015 34

43 Monday 13 July 2015 33

44 Monday 20 July 2015 32

45 Monday 27 July 2015 31

46 Monday 3 August 2015 30

47 Monday 10 August 2015 29

48 Monday 17 August 2015 28

49 Monday 24 August 2015 27

50 Monday 31 August 2015 26

51 Monday 7 September 2015 25

52 Monday 14 September 2015 24

53 Monday 21 September 2015 23

54 Monday 28 September 2015 22

55 Monday 5 October 2015 21

56 Monday 12 October 2015 20

57 Monday 19 October 2015 19

58 Monday 26 October 2015 18

59 Monday 2 November 2015 17

60 Monday 9 November 2015 16

61 Monday 16 November 2015 15

62 Monday 23 November 2015 14

63 Monday 30 November 2015 13

64 Monday 7 December 2015 12

65 Monday 14 December 2015 11

66 Monday 21 December 2015 10

67 Monday 28 December 2015 9

68 Monday 4 January 2016 8

69 Monday 11 January 2016 7

70 Monday 18 January 2016 6

71 Monday 25 January 2016 5

72 Monday 1 February 2016 4

73 Monday 8 February 2016 3

74 Monday 15 February 2016 2

75 Monday 22 February 2016 1

76 Monday 29 February 2016 0

I never realized that the

I never realized that the century years not divisible by 400 were not leap years. Thanks for the new info, like where have I been!? Please explain how our calendar adjusts for this. I thought that our calendar required a leap EVERY 4 years to stay in sync. Anxious for your reply. Thanks, Grant

The tropical year

The Editors's picture

The tropical year (essentially, the cycle of seasons, or how long it takes the Earth to orbit around the Sun) is about 365.2422 days long (rounded up to nearest ten thousandth). The Gregorian calendar is usually 365 days long. To compensate for the "0.2422" day (slightly under a quarter of a day each year) to keep in tune with the seasons, the calendar adds a "leap" day every four years, except when century years are not divisible by 400. With this rule, 97 leap days are added every 400 years, which means the average length of year in the Gregorian calendar is 365.2425 days.

The skipping of certain centuries helps to keep the calendar more in step with the tropical year. Although 365.2425 is still a bit ahead of the tropical year, it won't be out of step a full day until about 3300 years.

If we didn't have this extra "divisible by 400" rule, the average year in the Gregorian calendar would be 365.25 days instead of 365.2425, which means the calendar would even more quickly become out of step by a day with the tropical year (in about 128 years).