3 Ways to Calculate Leap Years - wikiHow (2024)

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1Using Division

2Checking a Calendar

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Reviewed byJoseph Meyer

Last Updated: August 27, 2023Fact Checked

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Leap years are a way to ensure that our calendar is on track. There are roughly 365.24 days in a year, which means that we need to add 1 extra day once every 4 years, and a year with 1 extra day is known as a leap year. We need to do this to ensure that we don't fall several hours behind each year. Calculating leap years is easy, but there are a few special rules to keep in mind as you do your calculations. If you prefer to look at a calendar instead of doing the math, then this is also an option.

Method 1

Method 1 of 2:

Using Division

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  1. 1

    Identify the year you want to check. Calculating leap years requires having a year that you want to check. Use a past year, the current year, or a future year as your starting point.[1]

    • For example, you could start by checking 1997 or 2012 if you want to look at a past year, or go with 2019 to check the current year, or select 2025 or 2028 to check a future year.
  2. 2

    See if the number is evenly divisible by 4. Dividing the year by 4 will result in a whole number with no remainder if the number is evenly divisible. The number must be evenly divisible by 4! Otherwise, it is not a leap year.[2]

    • For example, dividing 1997 by 4 gives you 499.25, which is not a whole number because it ends with a decimal. Therefore, it is not a leap year.
    • When you divide 2012 by 4, you get 503, which is a whole number. This means that 2012 is likely a leap year.

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  3. 3

    Confirm the number isn't evenly divisible by 100. If a year is evenly divisible by 4, but it is not evenly divisible 100, then it is a leap year. If a year is divisible by both 4 and 100, then it might not be a leap year, and you will have to perform 1 more calculation to check.[3]

    • For example, 2012 is evenly divisible by 4, but not 100 since it results in a decimal answer (20.12). This means that 2012 is definitely a leap year.
    • 2000 is divisible by 4 and it is also evenly divisible by 100 since it leaves a result of 20. That means that 2000 might not be a leap year and you will have to divide it 1 more time.
  4. 4

    Check if the number is evenly divisible by 400 to confirm a leap year. 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.[4]

    • 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.
    • On the other hand, 2000 is evenly divisible by 100 and 400, since it gives you a result of 5. That means that the year 2000 is a leap year.

    Tip: If you don’t want to manually divide a number to check it, or if you are unsure of your results, use an online leap year calculator. This will do the calculations for you.[5]

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  1. 1

    Locate the year you want to know about in a calendar.[6] Start by identifying the year that you want to check and then get out a physical calendar or open an online calendar to check that year. If you are using an online calendar, then you should be able to look back or ahead by at least a few years.[7]

    • For example, if you want to see if 2016 was a leap year, go back to that year’s calendar.
    • If you want to check if 2021 is a leap year, go to that year online.
  2. 2

    Turn to February and see if there is a 29th day. Leap years always result in 1 extra day that is placed at the end of February, since this is the shortest month in the year. Turn to that month in the calendar and check to see if there is a February 29th listed. If there is, then it is a leap year.[8]

    • If February only goes through the 28th, then it is not a leap year.
  3. 3

    Expect another leap year in 4 years. Each year lasts about 365 days and slightly under 6 hours. That extra 6 hours adds up to an extra day over the course of 4 years, which is why leap years occur almost every 4 years. Count ahead 4 years from the last leap year to estimate when the next leap year will be.[9]

    • For example, since 2016 was a leap year, you could count ahead 4 years to 2020 as a way to predict the next leap year.

    Tip: Keep in mind that sometimes there won’t be a leap year for 8 years since there is a little less than 6 extra hours each year—5 hours, 48 minutes, and 46 seconds to be exact.[10] That is why it is helpful to do calculations instead of relying on a leap year every 4 years.

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  • Question

    Why do we check for divisibility by 100? Is it not enough to check divisibility by 4?

    3 Ways to Calculate Leap Years - wikiHow (14)

    Community Answer

    No, there is still a small error that must be accounted for. To eliminate this error, the Gregorian calendar stipulates that a year that is evenly divisible by 100 (for example, 1900) is a leap year only if it is also evenly divisible by 400. For this reason, the following years are not leap years: 1700, 1800, 1900, 2100, 2200, 2300, 2500, 2600. This is because they are evenly divisible by 100 but not by 400.

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  • Question

    Why do we have leap years?

    3 Ways to Calculate Leap Years - wikiHow (15)

    Community Answer

    Each year is technically 12 months and a fraction of a day, close to .25. Every four years, the fraction is compiled to create a whole day and added to that year.

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  • Question

    Why specifically divided by 4, 100, and 400?

    3 Ways to Calculate Leap Years - wikiHow (16)

    Community Answer

    These numbers resulted from complex calculations that were done to ensure that, over the long term, our calendar years would stay as close as possible to the actual time it takes the earth to revolve around the sun. This includes somewhat arbitrary additions/subtractions of an extra day to certain years. Generally speaking, leap years occur every 4 years, and they are the years divisible by 4 (2000, 2004, 2008, etc.). However, for three out of four years divisible by 100, the leap year thing is skipped; only those years divisible by 100 that are also divisible by 400 remain leap years (so: 1600 was a leap year, while 1700, 1800, and 1900 were not; 2000 was a leap year, while 2100, 2200, and 2300 will not be).

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      About This Article

      3 Ways to Calculate Leap Years - wikiHow (29)

      Reviewed by:

      Joseph Meyer

      Math Teacher

      This article was reviewed by Joseph Meyer. Joseph Meyer is a High School Math Teacher based in Pittsburgh, Pennsylvania. He is an educator at City Charter High School, where he has been teaching for over 7 years. Joseph is also the founder of Sandbox Math, an online learning community dedicated to helping students succeed in Algebra. His site is set apart by its focus on fostering genuine comprehension through step-by-step understanding (instead of just getting the correct final answer), enabling learners to identify and overcome misunderstandings and confidently take on any test they face. He received his MA in Physics from Case Western Reserve University and his BA in Physics from Baldwin Wallace University. This article has been viewed 852,379 times.

      176 votes - 71%

      Co-authors: 22

      Updated: August 27, 2023

      Views:852,379

      Categories: Featured Articles | Time Management

      Article SummaryX

      To calculate whether or not a year is a leap year, start by checking if the number is evenly divisible by 4 since leap years need to be. Then, if it is evenly divisible by 4, check to see if it's evenly divisible by 100. If it's not, then it's a leap year. However, if it is evenly divisible by both 100 and 4, it might still be a leap year. To check, see if the year is evenly divisible by 400. If it is, then it's a leap year. To learn how to check to see if a year is a leap year using a calendar, scroll down!

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      3 Ways to Calculate Leap Years - wikiHow (2024)

      FAQs

      3 Ways to Calculate Leap Years - wikiHow? ›

      Check if the number is evenly divisible by 400 to confirm a leap year. 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.

      How do you calculate leap year easily? ›

      Determining Leap Years

      To determine if a year is a leap year, we apply a simple rule: if the year is divisible by 4, it's a leap year, except for end-of-century years, which must also be divisible by 400. For instance, the year 2000 was a leap year, while 1900 was not.

      What are the three rules for leap years? ›

      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.

      How is a leap year calculated answer? ›

      A leap year has 366 days (the extra day is the 29th of February), and it comes after every four years. To check if a year is a leap year, divide the year by 4. If it is fully divisible by 4, it is a leap year. For example, the year 2016 is divisible 4, so it is a leap year, whereas, 2015 is not.

      What are the conditions to calculate leap year? ›

      A leap year can be checked by dividing the year by 4. If the year is completely divisible, then it is a leap year. A century year on the other hand should be exactly divisible by 400 to be a leap year.

      How to find leap year in reasoning? ›

      Any year that is evenly divisible by 4 is a leap year: for example, 1988, 1992, and 1996 are leap years.

      How to find leap years in 100 years? ›

      The given year is divided by 4, and the quotient gives the number of leap years. But here 100 is not a leap year so we have to subtract the 100th year from the 25. So, 24 leap years in 100 years. Hence, the correct answer is "24 leap year".

      What happens if you are born on February 29 legally? ›

      When it comes to legal documents, such as obtaining a passport or driver's license, the date February 29th is recognized as the official birthday for leaplings in most countries. However, some states in the U.S. allow the leapling to celebrate their birthday on either February 28th or March 1st on non-leap years.

      Is 2024 a leap year, yes or no? ›

      Yes, 2024 is a leap year. For the first time since 2020, we have an extra day in February. This year, Leap Day falls on Thursday, February 29, 2024. The next time the shortest month of the year will get an extra day will be in 2028, so make sure to savor the extra day while we've got it!

      Is 2024 a true or false leap year? ›

      Here are some frequently asked questions about leap day and leap years: Is 2024 a leap year? Yes, 2024 is a leap year. It consists of 366 days instead of the usual 365 days.

      How did we figure out leap year? ›

      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.

      What are the rules for leap year? ›

      If the year is divisible by four, it's a leap year. But if the year can be divided by 100 as well as four, it's not a leap year. However, if the year is divisible by 400, it is a leap year. This system keeps the calendar aligned with the Solar year to within a few decimal places of accuracy.

      What is the algorithm for leap year? ›

      The algorithm to determine if a year is a leap year is 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.

      How to calculate the number of leap years between two years? ›

      For a year to be a leap year, it has to be divisible by 4. For century years however, the year must be divisible by 400 to be a leap year. For example, 2000 was a leap year, but 2100 will not be one. Every 400-year period has three centuries that have 24 leap years each and one century that has 25 leap years.

      How do leap year babies age legally? ›

      When it comes to legal documents, such as obtaining a passport or driver's license, the date February 29th is recognized as the official birthday for leaplings in most countries. However, some states in the U.S. allow the leapling to celebrate their birthday on either February 28th or March 1st on non-leap years.

      How do leap year babies count their age? ›

      His legal thinking is that February 29 is the day after February 28, so a person born on February 29 is legally considered to have aged one year on the day after February 28. In non-leap years, that day is March 1.

      Why is 1700 not a leap year? ›

      The Rule: According to the Gregorian calendar, which is the civil calendar in use today, years evenly divisible by 4 are leap years, with the exception of centurial years that are not evenly divisible by 400. Therefore, the years 1700, 1800, 1900 and 2100 are not leap years, but 1600, 2000, and 2400 are leap years.

      How do you calculate the number of leap years between two dates? ›

      For a year to be a leap year, it has to be divisible by 4. For century years however, the year must be divisible by 400 to be a leap year. For example, 2000 was a leap year, but 2100 will not be one. Every 400-year period has three centuries that have 24 leap years each and one century that has 25 leap years.

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