Thumbing through my iPhone I was curious and wondered what day I was born on. I thumbed back to 1956 and discovered I was a Tuesday baby. Knowing this now I was again bored and thumbed forward in time finding out my birthday would again occur on a Tuesday in 2023.
Thinking I might have something fun to do for a few more seconds I went forward further in time and randomly stopped on the year 2496. I noticed the February month had 29 days showing a leap year. Then something remarkable happened. I went forward another four years to 2500 and Hmmm, no Feb 29th! I flipped it to 2501 thinking I must have missed it. Nope. 2502? No again. 2503? No. 2504? Yes! That was eight years!
I thumbed back from 2496 to 2492, leap year. Forward to 2504, leap year.
Well sonubeech!
Research into leap years I had always learned was every four years was not quite correct.
What Is a Leap Year?
Leap years are years where an extra, or intercalary, day is added to the end of the shortest month, February. The intercalary day, February 29, is commonly referred to as leap day.
Leap years have 366 days instead of the usual 365 days and occur almost every four years.
Almost every four years? I'm now intrigued.
Why Do We Have Leap Years?
Leap days keep our modern-day Gregorian calendar in alignment with Earth's revolutions around the Sun. It takes Earth approximately 365.242189 days, or 365 days, 5 hours, 48 minutes, and 45 seconds, to circle once around the Sun. This is called a tropical year, and it starts on the March equinox.
However, the Gregorian calendar has only 365 days in a year. If we didn't add a leap day on February 29 almost every four years, each calendar year would begin about 6 hours before the Earth completes its revolution around the Sun (see illustration).
As a consequence, our time reckoning would slowly drift apart from the tropical year and get increasingly out of sync with the seasons. With a deviation of approximately 6 hours per year, the seasons would shift by about 24 calendar days within 100 years. Allow this to happen for a while, and Northern Hemisphere dwellers will be celebrating Christmas in the middle of summer in a matter of a few centuries.
Leap days fix that error by giving Earth the additional time it needs to complete a full circle around the Sun.
Leap Year Rules: How to Calculate Leap Years
In the Gregorian calendar, three criteria must be taken into account to identify leap years:
*1 The year must be evenly divisible by 4;
*2 If the year can also be evenly divided by 100, it is not a leap year;
unless...
*3 The year is also evenly divisible by 400. Then it is a leap year.
According to these rules, the years 2000 and 2400 are leap years,
while 1800, 1900, 2100, 2200, 2300, and 2500 are not leap years.
Wanna talk about the leap second?
Thinking I might have something fun to do for a few more seconds I went forward further in time and randomly stopped on the year 2496. I noticed the February month had 29 days showing a leap year. Then something remarkable happened. I went forward another four years to 2500 and Hmmm, no Feb 29th! I flipped it to 2501 thinking I must have missed it. Nope. 2502? No again. 2503? No. 2504? Yes! That was eight years!
I thumbed back from 2496 to 2492, leap year. Forward to 2504, leap year.
Well sonubeech!
Research into leap years I had always learned was every four years was not quite correct.
What Is a Leap Year?
Leap years are years where an extra, or intercalary, day is added to the end of the shortest month, February. The intercalary day, February 29, is commonly referred to as leap day.
Leap years have 366 days instead of the usual 365 days and occur almost every four years.
Almost every four years? I'm now intrigued.
Why Do We Have Leap Years?
Leap days keep our modern-day Gregorian calendar in alignment with Earth's revolutions around the Sun. It takes Earth approximately 365.242189 days, or 365 days, 5 hours, 48 minutes, and 45 seconds, to circle once around the Sun. This is called a tropical year, and it starts on the March equinox.
However, the Gregorian calendar has only 365 days in a year. If we didn't add a leap day on February 29 almost every four years, each calendar year would begin about 6 hours before the Earth completes its revolution around the Sun (see illustration).
As a consequence, our time reckoning would slowly drift apart from the tropical year and get increasingly out of sync with the seasons. With a deviation of approximately 6 hours per year, the seasons would shift by about 24 calendar days within 100 years. Allow this to happen for a while, and Northern Hemisphere dwellers will be celebrating Christmas in the middle of summer in a matter of a few centuries.
Leap days fix that error by giving Earth the additional time it needs to complete a full circle around the Sun.
Leap Year Rules: How to Calculate Leap Years
In the Gregorian calendar, three criteria must be taken into account to identify leap years:
*1 The year must be evenly divisible by 4;
*2 If the year can also be evenly divided by 100, it is not a leap year;
unless...
*3 The year is also evenly divisible by 400. Then it is a leap year.
According to these rules, the years 2000 and 2400 are leap years,
while 1800, 1900, 2100, 2200, 2300, and 2500 are not leap years.
Wanna talk about the leap second?
