Why Do We Have Leap Years?

So it's February 29th and we have 366 days this year instead of 365- what's the deal with Leap Years?

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Hosted by: Hank Green

Sources:

[PanozGTR]

0:47 I think it is important to note that the 'days' referred to in this entire video are mean solar days (the average time it takes for the sun to reach the same position in the sky), while this definition is actually that of sidereal days, a very slightly shorter amount of time. Long enough, however, that there is (exactly) one more sidereal days in the year than solar days.

[cfltheman]

The Julian calendar was off by 10 days in 1582 when the Gregorian calendar was introduced. The Julian calendar is now off by 13 days.

[chillsahoy]

Nice attention to detail, making the Earth's orbit slightly elliptical and slightly off-centre. The whole SciShow and SciShow Space team is fantastic!

[StopChangingMyNameYoutube]

Billy: Today I'm 21! I'm old enough to drink...Legally!
Mom: Silly Billy, you were born on a leap year, that means your only 5 and a quarter years old according to my calendar
Billy: It doesn't work that way ma
Mom: Have fun at kindergarten!
Billy: Ma!

[zeromancer-x]

Most comprehensive explanation for a leap year I've ever heard, thanks guys

[darkmage]

I'm in favor of switching over to Stardates as the new calendar.

[ganaraminukshuk]

Rules for the Gregorian calendar:
- Add an extra day every 4 years
- Don't add an extra day if the year is divisible by 100
- Add it back if it's divisible by 400

Imagine being born on 29 Feb 1896 and trying to celebrate your birthday on 29 Feb 1904. That's a whole new kind of leap year baby. (This won't happen again until 2096 and 2104.)

[EpicB]

We have leap years so every February 29, we can get out our seats and jump around.

[CoL_Drake]

when you already know the answer but just watch it cause of hank xD

[AlecThePirateKing]

Whenever there's a leap year, I can only think of the paradox song from Pirates of Penzance. "Though counting in the usual way, years twenty-one I've been alive. Yet reckoning by my natal day, yet reckoning by my natal day...I AM A LITTLE BOY OF FIVE!"

[EQuivalentTube]

0:15 Missed a perfect opportunity for Game of Thrones pun

[GraveUypo]

ugh FINALLY got to know what happens with that 0, 05 day a year. thank you

[Hermboldt]

Hey SciShow! Love you guys ! I'm a big fan and I have to ask if you guys have ever made mind/conscious videos? It would be great to have some elaboration on topics like that. Also, I've always been curious about how/why humans can hear our own
thoughts.

[michaeljordan]

My kid just turned 1 today 4 years ago.

[JacekJurewicz]

A day is not exactly one rotation, there's one more rotation per year than the number of days.
Also, the Julian calendar is currently 13 days behind.

[isabelagusmao]

"the universe doesn't care about our calendars" now that's comforting

[cloudkitt]

Here's the part I never understand, how did people back then know how and why the calendar was off? I get that after a couple centuries you would notice that your seasons are misaligned, but they apparently knew about the issues in advance and just chose not to deal with them. ...but how did they know about them?

[ClockworkRBLX]

1:10
"The earth orbits the sun every 365.2425 rotations"

That number is actually 365.2422 rotations.

[RJTheHero]

Oh, god. This makes leap year birthdays a pain to figure out. 😕

[epicvasu]

This video is so informative. I’ve learnt a lot of new things today.