September 5, 2025 • 11 mins
Trains, telegraphs, and global trade turned local solar time into a worldwide system, yet the story didn’t stop at 24 neat slices. In this Flashcards! episode, we explore why there are more than 24 time zones, how half-hour and 45-minute offsets came to be, how the International Date Line adds extra zones, why the North Pole has no official time, and how you’d pick a clock for a polar meeting (with a nod to Nunavut coffee culture near the top of the world).
G.M.T.- Great Mini Takeaways
- Prime Time: Why the “24-zone” model grew to include half-hour and 45-minute offsets.
- Date Line Design: How zigzags in the Pacific create “tomorrow” (and even UTC+14).
- Polar Protocol: No time zone at the North Pole, so teams pick one and sync.
Links & Resources
- What is Greenwich Mean Time? Royal Museums Greenwich. Royal Museums Greenwich
- The International Date Line explained. Timeanddate.com. Time and Date
- Time in Kiribati (GILT/PHOT/LINT; includes UTC+14) Overview. Time and Date
- Samoa’s 2011 “skipped day” (time-zone shift) Wired magazine. WIRED
- Alert, Nunavut (northernmost continuously inhabited place) Background. .css-j9qmi7{display:-webkit-box;display:-webkit-flex;display:-ms-flexbox;display:flex;-webkit-flex-direction:row;-ms-flex-direction:row;flex-direction:row;font-weight:700;margin-bottom:1rem;margin-top:2.8rem;width:100%;-webkit-box-pack:start;-ms-flex-pack:start;-webkit-justify-content:start;justify-content:start;padding-left:5rem;}@media only screen and (max-width: 599px){.css-j9qmi7{padding-left:0;-webkit-box-pack:center;-ms-flex-pack:center;-webkit-justify-content:center;justify-content:center;}}.css-j9qmi7 svg{fill:#27292D;}.css-j9qmi7 .eagfbvw0{-webkit-align-items:center;-webkit-box-align:center;-ms-flex-align:center;align-items:center;color:#27292D;}Mark as PlayedTranscript
Episode Transcript
Available transcripts are automatically generated. Complete accuracy is not guaranteed.
(00:01):
It's Flashcards Friday at Math, Science, History, and if you had a chance to listen
to Tuesday's podcast about the history of time, this serves as the perfect dessert for
the end of the week, Tim Horton style.
Today we're taking a closer look at the strange and wonderful world of time zones, and what
(00:22):
does this have to do with Tim Hortons? Well, stick with me, you will soon find out.
Before we had time zones, time was a local affair. Noon was simply when sun was at its
highest point in your sky. That means every town, sometimes even neighboring towns, could
be operating on a slightly different clock, which worked fine until trains, telegraphs,
(00:45):
and cross-country business entered the picture.
In the 1800s, as railroads began crossing entire countries, chaos ensued. Train companies
had to publish different timetables for every station on the line, each reflecting local
solar time. Imagine trying to plan a cross-country trip with 50 different clocks.
(01:07):
So in 1884, representatives from 26 nations met in Washington, D.C. at the International
Meridian Conference. Their goal? To standardize global time. The solution? Divide the world
into 24 time zones, each roughly 15 degrees of longitude apart, and designate one central
(01:29):
reference point, Greenwich, England, the home of the Royal Observatory, as the prime meridian
that is 0 degrees longitude. This gave birth to Greenwich Mean Time, or as we refer to
it as GMT.
So how do time zones work exactly? Each time zone represents 15 degrees of longitude, because
(01:51):
the Earth rotates 360 degrees in 24 hours. Divide 360 by 24 hours, and you get 15 degrees
per hour, meaning the Earth spins one time zone every 60 minutes. So, if you move east
of Greenwich, time moves forward. If you move west of Greenwich, time moves backwards.
(02:16):
So let's break it down with a formula that you can visualize. Local time equals GMT plus
the number of time zones times one hour. So, if you live in Los Angeles, like I do, which
is GMT 8, and it is 6 p.m. your time, add 8 hours to get GMT. So that would be 6 p.m.
(02:37):
plus 8 hours is 2 a.m. GMT. Now let's flip it. If you know it's 3 p.m. GMT and you want
to know what time it is in Mumbai, add 5 hours and 30 minutes. So that's 3 p.m. plus 5 hours
and 30 minutes, which is 8.30 p.m. Mumbai time. You might think there are only 24 hours
(02:59):
in a day, but here is a twist. The world actually has more than 24 time zones. When the world
standardized time in the 19th century, the globe was divided into 24 slices, one for
every hour of Earth's rotation. It sounds simple, right? But humans are not so simple.
(03:21):
Borders, politics, and practicality turned that neat little system into something much
messier. Today, there are more than 38 time zones when you count the half hour and quarter
hour offsets. That means while most countries follow neat one-hour steps from Greenwich
Mean Time or UTC, its modern version, others split the difference. So let's meet the 30-minute
(03:49):
and 45-minute rebels. Who bends the rules? Well, India sits proudly at UTC plus 5 hours
and 30 minutes. That half hour keeps New Delhi in sync with the rest of the country while
avoiding a split between East and West. Nepal goes a little further, landing at UTC plus
(04:10):
5 hours and 45 minutes. Yeah, a 45-minute increment. It's the only country in the world
to use one. Australia has multiple half hour zones like South Australia at UTC plus 9 hours
and 30 minutes. Then, Newfoundland in Canada is another example, running on UTC minus 3
(04:34):
hours and 30 minutes. So why do this? Well, it's all about local convenience and national
identity. Time is political as much as it is astronomical. And if half hour zones weren't
confusing enough, let's add the International Date Line. This International Date Line runs
(04:57):
down the Pacific Ocean opposite Greenwich, but it zigzags wildly to keep island nations
on the same calendar day as their neighbors. And this is where things get strange. On one
side of the line, it might be Monday morning. Just a few miles away across the line, it's
still Sunday morning. That split creates extra time zones beyond the basic 24 hours.
(05:22):
To the west of the line, you find UTC plus 12 hours. To the east of the line, you find
UTC minus 12 hours. And here's the kicker. Pacific nations like Kiribati decided they
didn't want their islands split across different days. So they created a UTC plus 14 hour zone,
(05:44):
which means they are the very first to welcome the new year. In fact, back in 2011, Samoa
jumped from UTC minus 11 hours to UTC plus 13 hours overnight, literally skipping an
entire Friday just to better align with business partners in Australia and New Zealand. So
(06:06):
imagine going to bed Thursday night and waking up Saturday morning, Friday completely banished
from the calendar, which means no flashcard Fridays for them, their loss. So thanks to
date lines, creative zigzagging, we end up with three more zones, UTC minus 12 hours,
(06:30):
UTC plus 13 hours, and UTC plus 14 hours. So if every zone followed only whole hours,
the math would be clean. But geography doesn't care about neat lines, and humans care about
daylight. By tweaking time with half hour or quarter hour offsets, governments keep sunrise,
(06:51):
sunset and business hours practical. That's why we say there are more than 24 hours in a day.
It's not that the earth spins slower, it's that our clocks are adjusted for human life.
Now, let's push timekeeping to the extreme. Let's say you have a meeting with Santa at the
(07:12):
North Pole. You could tell Santa that the meeting will be at 3pm, but he shows up at 5pm and he
says he's on time. Guess what? He's right. Why is that? Well, in the North Pole, time zones
completely disappear. That's because all lines of longitude converge there, which means technically
every time zone passes through the pole. In practice, there's no official time zone at all.
(07:37):
Researchers and explorers simply pick one, often UTC or the time zone of their home base.
So if you plan a meeting at the pole, coordination depends on agreement, not geography.
Okay, so maybe the North Pole is too extreme. Maybe you do have a meeting close to the North Pole.
(07:59):
Where are you going to eat? Well, just eight degrees south of the North Pole in Alert,
Nunavut, Canada, there is a Tim Hortons. Yes, this is the northernmost Tim Hortons in the world,
which in my opinion, would be worth going to Alert, Nunavut, Canada. And this is not a paid
(08:22):
advertisement, but Tim Hortons has the world's best coffee. So if you do have a meeting near the
North Pole, you can do it over a double double and some tin bits and their delicious, amazing,
incredible coffee. Oh, hey, speaking of coffee, come on by mathsciencehistory.com and click on
(08:44):
that coffee button and make a donation to Math Science History because every donation that you
make keeps this educational podcast and blog up and running. So here are our flashcards for the
weekend. One, the world agreed on 24 time zones in 1884. But today there are more than 38. Two,
(09:07):
some countries use half hour or even 45 minute offsets to fit their lives better. Three, at the
North Pole, time zones vanish, you get to choose one. And if you're in Alert, Nunavut, Canada, every
hour is coffee hour at Tim Hortons. Four, Tim Hortons has the best coffee ever. Before I wrap up
(09:32):
today's episode, I have something very exciting to share. After six incredible years of Math
Science History, my team and I are taking a well-deserved one week break before we start
season seven. So get out your dance pants because we're gonna have Dance Pants Friday every day
next week. What, you ask? What's that about? Well, I'm gonna tell you. We've got a special Spotify
(09:57):
playlist for you filled with some of our favorite music to celebrate Math Science History and keep
you at the nerd party while we are recharging. It is a public playlist. And if you have a favorite
nerd song, please add it to the playlist. Let's keep it going all season long. I can't wait to
(10:17):
hear what you add to it. You will find the link in our show notes. And I'll be mentioning it again
and again, because I want to see what you guys are adding. And in one week, we will be back
launching with season seven. And we are so excited to share it with you. Until next time,
carpe diem, carpe abdominem et celebramus. Seize the day, seize the week and party on.
(10:44):
So thank you for listening to the podcast for six wonderful years. And thank you to my amazing
growing team, David Aviles, my sound editor, Warren Birkman, my social media manager, and
my number one, Veronica Helmke, and my amazing and patient husband, Joe, who is so patient with me
(11:07):
every time I say, hold on, I just got to take care of this one more thing for the podcast.
Thank you, everybody, from the bottom of my heart for being part of this wonderful
mathematical, scientific, and historical journey. We'll see you in a week.
It's Flashcards Friday at Math, Science, History, and if you had a chance to listen
to Tuesday's podcast about the history of time, this serves as the perfect dessert for
the end of the week, Tim Horton style.
Today we're taking a closer look at the strange and wonderful world of time zones, and what
(00:22):
does this have to do with Tim Hortons? Well, stick with me, you will soon find out.
Before we had time zones, time was a local affair. Noon was simply when sun was at its
highest point in your sky. That means every town, sometimes even neighboring towns, could
be operating on a slightly different clock, which worked fine until trains, telegraphs,
(00:45):
and cross-country business entered the picture.
In the 1800s, as railroads began crossing entire countries, chaos ensued. Train companies
had to publish different timetables for every station on the line, each reflecting local
solar time. Imagine trying to plan a cross-country trip with 50 different clocks.
(01:07):
So in 1884, representatives from 26 nations met in Washington, D.C. at the International
Meridian Conference. Their goal? To standardize global time. The solution? Divide the world
into 24 time zones, each roughly 15 degrees of longitude apart, and designate one central
(01:29):
reference point, Greenwich, England, the home of the Royal Observatory, as the prime meridian
that is 0 degrees longitude. This gave birth to Greenwich Mean Time, or as we refer to
it as GMT.
So how do time zones work exactly? Each time zone represents 15 degrees of longitude, because
(01:51):
the Earth rotates 360 degrees in 24 hours. Divide 360 by 24 hours, and you get 15 degrees
per hour, meaning the Earth spins one time zone every 60 minutes. So, if you move east
of Greenwich, time moves forward. If you move west of Greenwich, time moves backwards.
(02:16):
So let's break it down with a formula that you can visualize. Local time equals GMT plus
the number of time zones times one hour. So, if you live in Los Angeles, like I do, which
is GMT 8, and it is 6 p.m. your time, add 8 hours to get GMT. So that would be 6 p.m.
(02:37):
plus 8 hours is 2 a.m. GMT. Now let's flip it. If you know it's 3 p.m. GMT and you want
to know what time it is in Mumbai, add 5 hours and 30 minutes. So that's 3 p.m. plus 5 hours
and 30 minutes, which is 8.30 p.m. Mumbai time. You might think there are only 24 hours
(02:59):
in a day, but here is a twist. The world actually has more than 24 time zones. When the world
standardized time in the 19th century, the globe was divided into 24 slices, one for
every hour of Earth's rotation. It sounds simple, right? But humans are not so simple.
(03:21):
Borders, politics, and practicality turned that neat little system into something much
messier. Today, there are more than 38 time zones when you count the half hour and quarter
hour offsets. That means while most countries follow neat one-hour steps from Greenwich
Mean Time or UTC, its modern version, others split the difference. So let's meet the 30-minute
(03:49):
and 45-minute rebels. Who bends the rules? Well, India sits proudly at UTC plus 5 hours
and 30 minutes. That half hour keeps New Delhi in sync with the rest of the country while
avoiding a split between East and West. Nepal goes a little further, landing at UTC plus
(04:10):
5 hours and 45 minutes. Yeah, a 45-minute increment. It's the only country in the world
to use one. Australia has multiple half hour zones like South Australia at UTC plus 9 hours
and 30 minutes. Then, Newfoundland in Canada is another example, running on UTC minus 3
(04:34):
hours and 30 minutes. So why do this? Well, it's all about local convenience and national
identity. Time is political as much as it is astronomical. And if half hour zones weren't
confusing enough, let's add the International Date Line. This International Date Line runs
(04:57):
down the Pacific Ocean opposite Greenwich, but it zigzags wildly to keep island nations
on the same calendar day as their neighbors. And this is where things get strange. On one
side of the line, it might be Monday morning. Just a few miles away across the line, it's
still Sunday morning. That split creates extra time zones beyond the basic 24 hours.
(05:22):
To the west of the line, you find UTC plus 12 hours. To the east of the line, you find
UTC minus 12 hours. And here's the kicker. Pacific nations like Kiribati decided they
didn't want their islands split across different days. So they created a UTC plus 14 hour zone,
(05:44):
which means they are the very first to welcome the new year. In fact, back in 2011, Samoa
jumped from UTC minus 11 hours to UTC plus 13 hours overnight, literally skipping an
entire Friday just to better align with business partners in Australia and New Zealand. So
(06:06):
imagine going to bed Thursday night and waking up Saturday morning, Friday completely banished
from the calendar, which means no flashcard Fridays for them, their loss. So thanks to
date lines, creative zigzagging, we end up with three more zones, UTC minus 12 hours,
(06:30):
UTC plus 13 hours, and UTC plus 14 hours. So if every zone followed only whole hours,
the math would be clean. But geography doesn't care about neat lines, and humans care about
daylight. By tweaking time with half hour or quarter hour offsets, governments keep sunrise,
(06:51):
sunset and business hours practical. That's why we say there are more than 24 hours in a day.
It's not that the earth spins slower, it's that our clocks are adjusted for human life.
Now, let's push timekeeping to the extreme. Let's say you have a meeting with Santa at the
(07:12):
North Pole. You could tell Santa that the meeting will be at 3pm, but he shows up at 5pm and he
says he's on time. Guess what? He's right. Why is that? Well, in the North Pole, time zones
completely disappear. That's because all lines of longitude converge there, which means technically
every time zone passes through the pole. In practice, there's no official time zone at all.
(07:37):
Researchers and explorers simply pick one, often UTC or the time zone of their home base.
So if you plan a meeting at the pole, coordination depends on agreement, not geography.
Okay, so maybe the North Pole is too extreme. Maybe you do have a meeting close to the North Pole.
(07:59):
Where are you going to eat? Well, just eight degrees south of the North Pole in Alert,
Nunavut, Canada, there is a Tim Hortons. Yes, this is the northernmost Tim Hortons in the world,
which in my opinion, would be worth going to Alert, Nunavut, Canada. And this is not a paid
(08:22):
advertisement, but Tim Hortons has the world's best coffee. So if you do have a meeting near the
North Pole, you can do it over a double double and some tin bits and their delicious, amazing,
incredible coffee. Oh, hey, speaking of coffee, come on by mathsciencehistory.com and click on
(08:44):
that coffee button and make a donation to Math Science History because every donation that you
make keeps this educational podcast and blog up and running. So here are our flashcards for the
weekend. One, the world agreed on 24 time zones in 1884. But today there are more than 38. Two,
(09:07):
some countries use half hour or even 45 minute offsets to fit their lives better. Three, at the
North Pole, time zones vanish, you get to choose one. And if you're in Alert, Nunavut, Canada, every
hour is coffee hour at Tim Hortons. Four, Tim Hortons has the best coffee ever. Before I wrap up
(09:32):
today's episode, I have something very exciting to share. After six incredible years of Math
Science History, my team and I are taking a well-deserved one week break before we start
season seven. So get out your dance pants because we're gonna have Dance Pants Friday every day
next week. What, you ask? What's that about? Well, I'm gonna tell you. We've got a special Spotify
(09:57):
playlist for you filled with some of our favorite music to celebrate Math Science History and keep
you at the nerd party while we are recharging. It is a public playlist. And if you have a favorite
nerd song, please add it to the playlist. Let's keep it going all season long. I can't wait to
(10:17):
hear what you add to it. You will find the link in our show notes. And I'll be mentioning it again
and again, because I want to see what you guys are adding. And in one week, we will be back
launching with season seven. And we are so excited to share it with you. Until next time,
carpe diem, carpe abdominem et celebramus. Seize the day, seize the week and party on.
(10:44):
So thank you for listening to the podcast for six wonderful years. And thank you to my amazing
growing team, David Aviles, my sound editor, Warren Birkman, my social media manager, and
my number one, Veronica Helmke, and my amazing and patient husband, Joe, who is so patient with me
(11:07):
every time I say, hold on, I just got to take care of this one more thing for the podcast.
Thank you, everybody, from the bottom of my heart for being part of this wonderful
mathematical, scientific, and historical journey. We'll see you in a week.
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