Leap years are one way to ensure that the calendar stays on track. There are approximately 365, 24 days in a year, which means that we need to add an extra day every 4 years and a year with 1 extra day is known as a leap year. We need to do this to make sure we are not delayed by several hours each year. Calculating leap years is easy, but there are some special rules to keep in mind when doing the calculations. If you prefer to look at the calendar instead of doing calculations, this is also an option.
Steps
Method 1 of 2: Use a Division
Step 1. Identify the year you want to verify
To calculate leap years requires a year that you want to verify. Use a past year, the current year, or a future year as a starting point.
For example, if you want to use a past year you can start by checking 1997 or 2012, or 2019 if you want to check the current year, or select 2025 or 2028 to check a future year
Step 2. Check if the number is divisible by 4
If the number is exactly divisible, the result of dividing it by four will be a whole number with no remainder. The number must be exactly divisible by 4! Otherwise, it is not a leap year.
- 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 5, you get 503, which is a whole number. This means that 2012 is likely to be a leap year.
Step 3. Confirm that the number is not exactly divisible by 100
If a year is exactly divisible by 4, but it is not exactly divisible by 100, then it is a leap year. If a year is divisible by 4 and 100, then it is probably not a leap year and you will have to do one more calculation to verify it.
- For example, 2012 is exactly divisible by 4, but not 100 because the result has decimals (20, 12). This means that 2012 is definitely a leap year.
- 2000 is divisible by 4 and it is also exactly divisible by 100, since you get a result of 20. That means 2000 is probably not a leap year and you will have to divide it one more time.
Step 4. Check if the number is exactly divisible by 400 to confirm that it is a leap year
If a year is divisible by 100, but not by 400, then "no" is a leap year. If a year is divisible by 100 and 400, then "if" is a leap year.
- For example, 1900 is exactly divisible by 100, but not by 400, since it yields a result of 4.75. This means that 1900 is not a leap year.
- On the other hand, 2000 is exactly divisible by 100 and 400, since it results in 5. That means that the year 2000 is a leap year.
tip: If you don't want to manually divide a number to verify it, or if you don't trust your results, use an online leap year calculator and it will do the math for you.
Method 2 of 2: Review a calendar
Step 1. Find the year you want to check on a calendar
Start by identifying the year you want to verify and then get a physical calendar or open an online calendar to review that year. If you use an online calendar, you will be able to verify several previous or future years.
- 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 online to that year.
Step 2. Check February to see if it has a 29 day
Leap years have 1 extra day that is placed at the end of February, as it is the shortest month of the year. Go to that month on the calendar and check to see if there is a 29th. If there is, then it is a leap year.
If February only goes through the 28th, then it is not a leap year
Step 3. Expect another leap year in 4 years
Each year lasts approximately 365 days and a little less than 6 hours. Those 6 extra hours add an extra day after 4 years, which is why leap years occur almost every 4 years. Count 4 years from the last leap year to estimate when the next will be.
For example, since 2016 was a leap year, you can count 4 more years to 2020 as a way to predict the next leap year
tipKeep in mind that sometimes there won't be a leap year for 8 years, as there are less than 6 overtime hours each year, 5 hours, 48 minutes, and 46 seconds to be exact. This is why it is useful to do calculations instead of trusting that there will be a leap year every four years.