All language subtitles for Johnny Harris - The International Date Line, Explained (720p).English

- A while back, I made a promise.

(soft music)

Someday, I'll make a video
about this whole messy debacle.

So today I intend to make
good on that promise.

Here we go.

(upbeat music)

This line is weird.

It's not a border,

but I guess it kind of
is, it divides something.

If it's Monday evening

and you fly from Hawaii to New Zealand,

you'll cross into Tuesday
evening and then back

into Monday evening and then
back into Tuesday evening.

And because you've been
flying for a while,

now it's probably Wednesday morning.

You just jumped

from Monday to Wednesday
on a nine hour flight.

Better yet, jump in your
boat on a Tuesday afternoon

and go a few hundred kilometers south.

And suddenly you're watching
the sunset on a Monday

because you drove south in your boat.

Wait what?

So I want to understand this line.

So naturally the first thing I do is go

into After Effects and try to map it out.

As I scoured the internet
for good data on this,

I realized that everyone's
international dateline

is slightly different,

from Google Maps to the CIA fact book,

to the Pacific Island
Ocean Observing System,

which is an organization
that has the elegant acronym

of PacIOOS.

Anyway, I spent the day
scraping all the data I could,

and trying to map this line.

Looks like it's 195 miles
or around 300 kilometers.

That's a huge difference.

There are entire islands
with people that Google

says are on one side and
PacIOOS say are on the other.

Who's right here?

Before we settle that,

I want to dig into what this line even is

and why it looks the way it does.

Okay, so this whole crossing a line

and passing over a day
and going back in time

and all of that, is a little bit hard

for I know my brain to get around.

And I imagine that a lot
of you came to this video,

hoping that you will leave this video

with a firm grasp of what The
International Date Line is.

So I'm going to dive in and
explain it the best I can.

First, let's look at
the earth from top down.

So we're looking at the earth
from above, like top down.

Here's great Britain over here.

And of course,

we've got our beautiful sun
shining light onto our earth

which gives us day and night.

Land that is rotating into
this light is seeing a sunrise,

land that is transitioning
out of this light

is seeing a sunset.

And it's the relationship

to this light that we
measure our time with,

with noon being the point
where we are right smack dab

in the middle of the sun's light.

So right now it's noon in Florida.

Okay, you already know this,
but I'm setting it up here

because it helps the
Date Line makes sense.

Let's go back to Britain,
which is upside down right now

because remember we're
looking down on the globe,

like we're looking down at the North Pole.

Also, this circle is pretty sloppy.

Let's clean it up and
make it a nice square

so you can keep your eye on it.

It's important because all
time is measured from here,

technically in a little
observatory called Greenwich.

So let's say, here in London,
it is the middle of the day,

on a Monday.

Okay, so it's noon on a Monday,

the sun is shining right on London.

So let's freeze time and
look what's happening

a few thousand kilometers east of here

in the middle of Russia, it's 6:00 PM.

The sun is setting.

It's still Monday, but the
sun is setting on Monday.

At this same moment, frozen in
time, over here in East Asia,

we've got China and there's Japan.

It's still noon in London, remember that,

but it's late over here.

The sun has gone down.

It's 9:00 PM in Japan.

It's still Monday.

It's just late.

The sun went down hours ago.

These people are finishing Monday.

It's like the middle
of the night on Monday.

It's noon in London.

Let's zoom out and
realize that it's Monday,

all around the world.

The more west you go from London

it is actually earlier on Monday.

East of London, it's
late on a Monday night,

like we just saw.

It's later and later the more east you go.

This is The International Date Line.

It divides whether or not
it's late on a Monday night

or early on a Monday morning.

Now let's press play

on the globe and watch
it rotate into a new day.

Remember that these
guys right here are like

at 11:00 PM, basically midnight.

They're about to start Tuesday.

I'll keep Monday as this orange circle

and I'll use green for Tuesday.

Okay, press play.

(upbeat music)

Okay stop, zoom in, here in
the middle of the Pacific.

It's almost 11:00 AM on Tuesday, right?

You're 12 hours ahead of
Greenwich Mean Time in London.

Go right over this line and
you'll still be around 11:00 AM.

The sun is still shining in the same way,

but now you are 12 hours
behind Greenwich Mean Time,

but it's still Monday.

You're 12 hours behind Greenwich.

It hasn't passed into a new day yet.

And that's how you're
able to cross this line

and go back a day or forward a day,

even though you only go
a few hundred kilometers.

Okay.

I'm sure you're tired of
looking at this top down globe.

It's kind of disorienting
and not super intuitive.

So let's see what this
looks like on a map,

on a regular old map.

Here we are in the same exact scenario.

It's around 11:00 AM right here.

And yet it's Tuesday here
and Monday over here.

I'm going to call this side which is later

than London's time, it's east
of London, the Tuesday side.

And I'm going to call this side,

which is behind London or west
of London, the Monday side.

I'll just use that, that's
my own little terminology.

I'm gonna start using that.

And no one else uses it like that,

but I'm just going to for
the rest of this video, okay.

I'm interrupting all of this
conceptual non-intuitive stuff

for a little intermission.

I want you to just look
at this for a second.

There are a bunch of beautiful
islands in the Pacific.

This one's called Aitutaki.

That's really what it's called.

That was my best accent.

Just remember that The
International Date Line runs

through some of the most
beautiful ocean in the world,

and it's worth just
looking at it for a second.

Let's get going on this
question of why it's different

on every map.

Why does this line look so messed up,

and what's with this notch?

And why can't anyone agree
on what it should look like?

This is the part that
I knew nothing about.

And it's fascinating.

Technically, according to
our little conceptual model

that we just did, the line
should just be like this,

a straight line that's on
the exact opposite side

of the world as Greenwich.

Meaning if Greenwich is zero,

this would be the 180th Meridian.

But as I've said many times before,

nature isn't super good at straight lines.

So instead it looks like this.

It starts out following the
180th Meridian as it should.

Then it splits off right here to make sure

that this Russian Island and
then the very eastern tip

of Russia don't get sliced in two,

to become part of different days.

As it accommodates Russia.

It passes right here
between Russia and Alaska.

If you zoom in,

you'll see that it passes right
through these two islands.

These islands are just
a few kilometers away

from each other.

The sun sets at the same
time on both these islands,

they're right next to each other.

The difference is the sun is setting

on a Tuesday here and on a Monday here.

After Russia, the line heads
back west to meet up with

the 180th, but it passes
it in order to keep all

of these islands on this side
because they belong to Alaska.

This notch goes all the way
over to accommodate this island

of Alaska, which is this
tiny outpost of 21 people.

It looks like the most western
part of the United States,

but really because it's on the other side

of the 180th Meridian,
everything left of this line

is actually in the Eastern hemisphere.

So this is technically
the eastern most part

of the US but whatever,
it doesn't really matter.

It's all, these are all fake lines anyway.

Okay, so we've zigzagged back and forth,

crossing the 180th Meridian a few times

to accommodate Russia
and the United States.

It finally gets back onto the 180th

and starts following it
south for a really long time.

Once it gets to the equator,
we begin the big game

of whose side are you on?

All these islands in the Pacific

and there are loads of them,

have to make a decision on whether

or not they want to be the
first people to start new days,

or the last people to end those days.

We've got this big notch here

which basically exists
to accommodate Kiribati,

which is an island nation
of just like 112,000 people.

But this nation is spread

across a huge swath of ocean,
which spans an area greater

than the continental United States.

It's huge.

It bounces around here to
make sure that Kiribati

is on the Eastern hemisphere time zone

with Australia and Asia,

and that other nations
like the Cook Islands

are on the western part,
like with the United States.

It dips down here between Samoa,

which is on the Tuesday
side and the islands

of American Samoa, which
are on the Monday side,

same with the United States.

From here, the line heads straight south,

but not along the 180th like it should,

instead it follows
closer to like the 172nd.

This has meant to allow a bunch

of these island nations to
stay in the Tuesday side

so that they can be on the same date

as big regional countries
like Australia or New Zealand.

Then finally it meets up
with the 180th Meridian

and it follows it all the
way down to Antarctica.

Okay.

So that is this line and why it exists

and why it zigzags and all
of its twists and turns.

So our two important questions here,

why does it look so weird,

and why is it different on every map?

The first one we can kind
of answer pretty easily

after seeing where the line goes,

which is this line is really flexible.

It's not a real border.

It doesn't denote any
land that somebody owns.

A regular border is defined

through conflict or negotiation,

and it denotes the
sovereignty of a country.

You own this and I own that.

That is what a normal border does.

This doesn't do that.

The Date Line is a decision

that every country can make for itself.

When they're in the
Pacific they can decide,

oh, I want to be on the same
date as Australia and Japan,

or I want to be on the same date as Hawaii

and the United States.

That is a unilateral decision

that no country has to
negotiate with others to make.

The Pacific nation of Samoa has decided

it would be better off if it observed

a time zone closer to that
of Australia and New Zealand.

So it's declared, it
will switch to our side

of The International Date Line

Before that big notch existed,

half of Kiribati was in the Tuesday side

and the other half was in the Monday side,

which just made it really
hard where it was like Friday

on this side, and if people wanted to get

in touch with people in their country,

it was already Saturday on their side

and so they were off for the weekend.

So they unilaterally decided
in 1995 to just change the line

and put the entire country
on the Tuesday side.

So every country decides
how they want to do it,

and because of that,
it's changed dramatically

over the years as countries
just make their own decision

on what date and times
that they want to be in.

So now to my second
question and the big one

that I was very curious
about which is who's right?

After a day of fixating on this question

and mapping and doing all
this stuff on the computer,

it all came down to this moment.

You have these two versions of
the notch that are different.

The black one is Google Maps.

This is how Google Maps displays it on all

of their different platforms.

And this yellow one is from that PacIOOS,

the Pacific observer something
I don't really remember,

but it's like a big authority
for the Pacific Ocean.

Remember that this is the Monday side

and this is the Tuesday side,
same time, different dates.

As I zoomed around this,
I saw these islands.

Google says that these islands are

on the Tuesday side, the
one day ahead inside.

Whereas PacIOOS says that
these are on the Monday side,

meaning the one day behind side.

I checked the official time zone

for every one of these islands,

and discover that they all
belong to the Cook Islands,

which is a set of islands
connected to New Zealand.

But that is on GMT minus 10,

meaning it's 10 hours behind GMT,

not a bunch of hours in front of GMT.

In short, all of these
islands are on Monday side.

PacIOOS has it right, and
Google Maps has it wrong.

Wait, what?

Google Maps has something wrong.

Bit of an existential
crisis I've been going

through the past couple of days.

I want to be wrong on this.

In fact, if somebody comments
and points out a flaw

in my logic or my analysis here,

I will be grateful for that,

because this is something that, I mean,

I have a really deep
appreciation for Google Maps

and all of the wonderful
mapping that they do,

but I think they got this wrong.

Somebody prove me wrong, please.

And if not, my world view
has just shifted slightly.

But here's the thing,
at the end of the day,

it doesn't really matter.

The fact that Google Maps
didn't painstakingly weave

it's line through all of these islands,

is kind of an indication
that these borders,

these fake borders, these
lines don't actually

do anything besides
describe the preference

on how different countries
want to measure their time.

It doesn't give anyone extra land.

It doesn't give anyone
extra waters or minerals

or any of this stuff

that usually make lines really important.

In this case, we're
describing a preference.

And so I'm sure that these
mapping organizations

haven't cared too much about
getting the shape perfectly

in this vast swath of ocean
that is mostly uninhabited.

That's The International Date Line.

I want to hear thoughts
and feedback from everyone

and thank you for watching.

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