* . *
  • About
  • Advertise
  • Privacy & Policy
  • Contact
Monday, October 6, 2025
Earth-News
  • Home
  • Business
  • Entertainment
    “Reba” cast, then and now: See the stars 24 years later (and who’s reunited for another show) – Yahoo

    “Reba” cast, then and now: See the stars 24 years later (and who’s reunited for another show) – Yahoo

    Why Taylor Swift Name-Dropped Elizabeth Taylor in Her New Album – Yahoo

    Here’s Why Taylor Swift Dropped Elizabeth Taylor’s Name in Her New Album

    Al Roker Gives Olivia Dean an Unexpected ‘New Job’ on the ‘Today’ Show – Yahoo

    Al Roker Shocks Olivia Dean with an Exciting New Role on the ‘Today’ Show

    Books about the arts and some haunts for a Denton October – Denton Record-Chronicle

    Uncover Artistic Treasures and Spooky Adventures to Experience in Denton This October

    Taylor Swift Releases New Album The Life of a Showgirl : Listen and Read the Full Credits – Yahoo

    Taylor Swift Releases New Album The Life of a Showgirl : Listen and Read the Full Credits – Yahoo

    Toni Braxton Is Turning Her Biggest Hits Into Lifetime Movies – Yahoo

    Toni Braxton Is Turning Her Biggest Hits Into Lifetime Movies – Yahoo

  • General
  • Health
  • News

    Cracking the Code: Why China’s Economic Challenges Aren’t Shaking Markets, Unlike America’s” – Bloomberg

    Trump’s Narrow Window to Spread the Truth About Harris

    Trump’s Narrow Window to Spread the Truth About Harris

    Israel-Gaza war live updates: Hamas leader Ismail Haniyeh assassinated in Iran, group says

    Israel-Gaza war live updates: Hamas leader Ismail Haniyeh assassinated in Iran, group says

    PAP Boss to Niger Delta Youths, Stay Away from the Protest

    PAP Boss to Niger Delta Youths, Stay Away from the Protest

    Court Restricts Protests In Lagos To Freedom, Peace Park

    Court Restricts Protests In Lagos To Freedom, Peace Park

    Fans React to Jazz Jennings’ Inspiring Weight Loss Journey

    Fans React to Jazz Jennings’ Inspiring Weight Loss Journey

    Trending Tags

    • Trump Inauguration
    • United Stated
    • White House
    • Market Stories
    • Election Results
  • Science
  • Sports
  • Technology
    Forget Cowbells. Cows Wear High-Tech Collars Now. – The New York Times

    Ditch the Cowbells: Discover the High-Tech Collars Transforming Cattle Care

    What the Recent Price Surge Means for Figure Technology Solutions After SEC Settlement – Yahoo Finance

    What the Recent Price Surge Reveals About Figure Technology Solutions Following SEC Settlement

    MAC Brings iPad Technology to Football Sidelines Across All 13 Member Schools – Sports Video Group

    MAC Brings iPad Technology to Football Sidelines Across All 13 Member Schools – Sports Video Group

    Technology Is Becoming More Important Than Humans In CX – No Jitter

    Technology Is Becoming More Important Than Humans In CX – No Jitter

    A Tech Expo Shows What China Can Make, but Not Who’ll Buy It All – The New York Times

    Inside China’s Tech Expo: Cutting-Edge Innovations Face Uncertain Demand

    Steampunk Metal Oval Technology Sense Sunglasses Personality Handmade Chain Multicolor Sunglasses UV400 – The San Joaquin Valley Sun

    Steampunk Metal Oval Sunglasses with Handmade Multicolor Chain – Bold UV400 Protection and Unique Style

    Trending Tags

    • Nintendo Switch
    • CES 2017
    • Playstation 4 Pro
    • Mark Zuckerberg
No Result
View All Result
  • Home
  • Business
  • Entertainment
    “Reba” cast, then and now: See the stars 24 years later (and who’s reunited for another show) – Yahoo

    “Reba” cast, then and now: See the stars 24 years later (and who’s reunited for another show) – Yahoo

    Why Taylor Swift Name-Dropped Elizabeth Taylor in Her New Album – Yahoo

    Here’s Why Taylor Swift Dropped Elizabeth Taylor’s Name in Her New Album

    Al Roker Gives Olivia Dean an Unexpected ‘New Job’ on the ‘Today’ Show – Yahoo

    Al Roker Shocks Olivia Dean with an Exciting New Role on the ‘Today’ Show

    Books about the arts and some haunts for a Denton October – Denton Record-Chronicle

    Uncover Artistic Treasures and Spooky Adventures to Experience in Denton This October

    Taylor Swift Releases New Album The Life of a Showgirl : Listen and Read the Full Credits – Yahoo

    Taylor Swift Releases New Album The Life of a Showgirl : Listen and Read the Full Credits – Yahoo

    Toni Braxton Is Turning Her Biggest Hits Into Lifetime Movies – Yahoo

    Toni Braxton Is Turning Her Biggest Hits Into Lifetime Movies – Yahoo

  • General
  • Health
  • News

    Cracking the Code: Why China’s Economic Challenges Aren’t Shaking Markets, Unlike America’s” – Bloomberg

    Trump’s Narrow Window to Spread the Truth About Harris

    Trump’s Narrow Window to Spread the Truth About Harris

    Israel-Gaza war live updates: Hamas leader Ismail Haniyeh assassinated in Iran, group says

    Israel-Gaza war live updates: Hamas leader Ismail Haniyeh assassinated in Iran, group says

    PAP Boss to Niger Delta Youths, Stay Away from the Protest

    PAP Boss to Niger Delta Youths, Stay Away from the Protest

    Court Restricts Protests In Lagos To Freedom, Peace Park

    Court Restricts Protests In Lagos To Freedom, Peace Park

    Fans React to Jazz Jennings’ Inspiring Weight Loss Journey

    Fans React to Jazz Jennings’ Inspiring Weight Loss Journey

    Trending Tags

    • Trump Inauguration
    • United Stated
    • White House
    • Market Stories
    • Election Results
  • Science
  • Sports
  • Technology
    Forget Cowbells. Cows Wear High-Tech Collars Now. – The New York Times

    Ditch the Cowbells: Discover the High-Tech Collars Transforming Cattle Care

    What the Recent Price Surge Means for Figure Technology Solutions After SEC Settlement – Yahoo Finance

    What the Recent Price Surge Reveals About Figure Technology Solutions Following SEC Settlement

    MAC Brings iPad Technology to Football Sidelines Across All 13 Member Schools – Sports Video Group

    MAC Brings iPad Technology to Football Sidelines Across All 13 Member Schools – Sports Video Group

    Technology Is Becoming More Important Than Humans In CX – No Jitter

    Technology Is Becoming More Important Than Humans In CX – No Jitter

    A Tech Expo Shows What China Can Make, but Not Who’ll Buy It All – The New York Times

    Inside China’s Tech Expo: Cutting-Edge Innovations Face Uncertain Demand

    Steampunk Metal Oval Technology Sense Sunglasses Personality Handmade Chain Multicolor Sunglasses UV400 – The San Joaquin Valley Sun

    Steampunk Metal Oval Sunglasses with Handmade Multicolor Chain – Bold UV400 Protection and Unique Style

    Trending Tags

    • Nintendo Switch
    • CES 2017
    • Playstation 4 Pro
    • Mark Zuckerberg
No Result
View All Result
Earth-News
No Result
View All Result
Home Science

Why Do We Have a Leap Year Anyway?

February 26, 2024
in Science
Why Do We Have a Leap Year Anyway?
Share on FacebookShare on Twitter

When I was a little kid I had a friend who was born on February 29, the “leap day” we add to that month every four years. I remember we used to tease him by saying that he was only three years old. I lost contact with him over the years, but I’d guess that by now he’s pretty sick of the joke.

And here we are again on the cusp of our quadrennial exercise in timekeeping: leap day 2024 is almost upon us. A handful of traditions have been associated with it; one held that this was the only acceptable day for—gasp!—women to propose marriage to men. Some folks like to treat this day as a free day that gives them time to catch up with something they’ve long been putting off.

I think that’s a pretty good idea because, after all, catching up is what leap day is all about—astronomically speaking, that is.

On supporting science journalism

If you’re enjoying this article, consider supporting our award-winning journalism by subscribing. By purchasing a subscription you are helping to ensure the future of impactful stories about the discoveries and ideas shaping our world today.

There are two basic units of time we use that are based on astronomical events. One is the day, the length of time it takes Earth to spin once on its axis. The other is the year, the time it takes for Earth to complete an orbit of the sun. While that seems simple, these two units are actually pretty complicated. For example, Earth spins once relative to what? You need some frame of reference against which to measure that motion.

For our daily life, we use the sun. The time it takes for the sun at due south to set and then rise again and reach the southern meridian once more is one solar day, which we define as 24 hours, or 86,400 seconds. This is actually the mean solar day, which uses the center of the sun’s disk as a reference point and is an average of every day of the year. Using an average value is helpful for timekeeping because Earth moves at different speeds at different points in its orbit, which changes the exact length of any particular day.

There are several different ways to measure the length of the year as well. Our current calendar uses the tropical year, the time from vernal equinox to vernal equinox, to account for subtle effects such as precession. Otherwise the date of the equinox would slowly change over the years, and eventually the December solstice would occur in July, which would be awfully confusing.

A tropical year is 365.2422 mean solar days in length. Because Earth’s rotation and orbital period are not linked in any way, they don’t divide evenly. We’re left with that 0.2422 remainder, and that’s the key to leap days.

If we start measuring the day and the year at the exact same moment, at the end of one year Earth will have spun 365 times, plus an extra 0.242 of the way around when the new year begins. After four years, that adds up to 0.9688 day—very nearly a full day. We’ve built up an extra day in the year!

This was known even to ancient peoples, and when Julius Caesar decided to change the basis of the Roman calendar from using the moon to the sun, he also decreed that every fourth year an extra day would be added to keep everything in sync. Congratulations! Happy leap day! This is technically called an intercalary day, one that is added to the calendar to sync it up.

Except the math doesn’t quite work out. By adding a whole day every four years, we’re adding too much: after four years we only have 0.9688 day left over, not 1.0 day. That difference is 0.0312 day, or about 45 minutes. That means every four years we still have about three quarters of an hour to account for. Over time, that’ll build up, and the calendar will be off again.

Enter Pope Gregory XIII, who reformed the calendar again in 1582. He decreed that every 100th year (to make it simple, years ending in 00) would not be a leap year, so no leap day would be added. There are 25 leap days in a century, so this method removes 25 x 0.0312=0.78 day, and the calendar syncs up a little bit better in the long run—but again, not exactly.

Using this algorithm, every 100 years the calendar will run 1 – 0.78=0.22 day behind. That adds up, too! So as part of his papal bull, Pope Gregory XIII also declared that every 400th year would once again acquire a leap day. By then there’s an extra 4 x 0.22=0.88 day, so adding one day gets us decently close to catching up with Earth’s irritatingly nonintegral annual-diurnal ratio.

That’s the rule we use now. Every fourth year, meaning every year whose number is evenly divisible by 4, is a leap year and is granted an extra day—that is, except for every 100 years, when we skip the leap day, except for every 400 years, when we reverse the rule and add a leap day once again. So the years 1700, 1800 and 1900 were not leap years. The year 2000 was because even though it’s divisible evenly by 100, it’s also evenly divisible by 400. The year 2100 will not be a leap year, but the year 2400 will be, and so on.

This actually gets us pretty close to synced up. I’ve sometimes wondered, though, why Pope Gregory XIII didn’t use the time span of every 500 years instead of 400. That would be better because the leftover amount after 100 years is closer to one fifth of a day. But here we are.

Because of this, though, our current rules still leave the calendar a wee bit off. We add a whole day every 400 years, but that’s too much by 1 – 0.88=0.12 day. If we wanted to, we could amend the rule again and say that every 3,200 years, we don’t make that year a leap year. Why 3,200? Well, 8 x 0.12=0.96, so we could skip a leap year every eighth 400-year cycle, which is every 3,200 years. That would mean that the year and day would only be off by 0.04 day—just under an hour—every three millennia, which is pretty danged close.

As usual, when dealing with astronomy and numbers and the calendar, things seem simple—until they aren’t.

So anyway, happy leap day, and if you have something that you’ve been putting off for four years, now is as good a time as any to get to it. And to my old friend Ted, if you’re out there and happen to see this: happy birthday!

>>> Read full article>>>
Copyright for syndicated content belongs to the linked Source : Scientific American – https://www.scientificamerican.com/article/why-do-we-have-a-leap-year-anyway/

Tags: anywayscience
Previous Post

A judge has rejected Trump’s request for late payment in the E. Jean Carroll case

Next Post

JWST Solves Decades-Old Mystery of Nearby Supernova

EarthTalk – Why do eco-advocates consider backyard gardens so crucial to conservation? – Kiowa County Press

How Backyard Gardens Are Becoming the Heart of Conservation Efforts

October 5, 2025
Citizen science discovers a rare bird in town | Opinion – Times Record News

Citizen science discovers a rare bird in town | Opinion – Times Record News

October 5, 2025
Millions could be living with hidden smell loss after COVID without knowing – ScienceDaily

Millions Could Be Unknowingly Struggling with Hidden Smell Loss Following COVID

October 5, 2025
How This Influencer Lost 31 Kg By Following These 8 “Weird” Daily Habits – NDTV

How This Influencer Lost 31 Kg By Following These 8 “Weird” Daily Habits – NDTV

October 5, 2025
Forget Cowbells. Cows Wear High-Tech Collars Now. – The New York Times

Ditch the Cowbells: Discover the High-Tech Collars Transforming Cattle Care

October 5, 2025
Tampa Bay Buccaneers vs. Seattle Seahawks NFL game: How to watch, kickoff time, TV channel and more – Yahoo Sports

Tampa Bay Buccaneers vs. Seattle Seahawks: How to Watch, Kickoff Time, TV Channel, and More

October 5, 2025
Magdeleine Vallieres shows off her world championship stripes – EF Pro Cycling

Magdeleine Vallieres shows off her world championship stripes – EF Pro Cycling

October 5, 2025
Splurging? In This Economy? Here’s How to Do It Right. – The New York Times

Splurging? In This Economy? Here’s How to Do It Right. – The New York Times

October 5, 2025
“Reba” cast, then and now: See the stars 24 years later (and who’s reunited for another show) – Yahoo

“Reba” cast, then and now: See the stars 24 years later (and who’s reunited for another show) – Yahoo

October 5, 2025
How the government shutdown is hitting the health care system – and what the battle over ACA subsidies means – The Conversation

How the Government Shutdown Is Disrupting Health Care and What the Battle Over ACA Subsidies Means for You

October 5, 2025

Categories

Archives

October 2025
M T W T F S S
 12345
6789101112
13141516171819
20212223242526
2728293031  
« Sep    
Earth-News.info

The Earth News is an independent English-language daily published Website from all around the World News

Browse by Category

  • Business (20,132)
  • Ecology (853)
  • Economy (873)
  • Entertainment (21,747)
  • General (17,430)
  • Health (9,915)
  • Lifestyle (886)
  • News (22,149)
  • People (875)
  • Politics (884)
  • Science (16,084)
  • Sports (21,374)
  • Technology (15,855)
  • World (856)

Recent News

EarthTalk – Why do eco-advocates consider backyard gardens so crucial to conservation? – Kiowa County Press

How Backyard Gardens Are Becoming the Heart of Conservation Efforts

October 5, 2025
Citizen science discovers a rare bird in town | Opinion – Times Record News

Citizen science discovers a rare bird in town | Opinion – Times Record News

October 5, 2025
  • About
  • Advertise
  • Privacy & Policy
  • Contact

© 2023 earth-news.info

No Result
View All Result

© 2023 earth-news.info

No Result
View All Result

© 2023 earth-news.info

Go to mobile version