Visualize the World's Rhythm
A complete dashboard of global time, exploring the history of how we measure our connected world.
The Story of Time Itself
Why do we have time zones? The answer lies in the age of steam and steel.
Before the 19th century, time was a local affair. Each town set its clocks by the sun's position at noon. This worked perfectly well for centuries. However, the invention of railways changed everything. Trains moving at unprecedented speeds made "local time" a logistical nightmare. A train traveling from Boston to New York would pass through numerous local time zones, making scheduling nearly impossible.
The solution was a standardized system. In 1884, at the International Meridian Conference in Washington, D.C., the globe was officially divided into 24 time zones. Greenwich, England was chosen as the prime meridian (0° longitude), establishing Greenwich Mean Time (GMT) as the world's time standard. This single decision synchronized the entire planet, paving the way for the globalized world we know today.
Crossing the Line: A Journey Through Time
The International Date Line is where tomorrow becomes yesterday.
Roughly following the 180° longitude meridian in the middle of the Pacific Ocean is the International Date Line (IDL). It's the official "seam" of the calendar day. When you cross it, you instantly travel forward or backward in time by one full day.
Traveling East (e.g., from Japan to the USA): As you cross the IDL, you "gain" a day. If you leave on a Saturday, you'll arrive on a Friday. You effectively get to live the same calendar day twice!
Traveling West (e.g., from the USA to Japan): Crossing the IDL in this direction means you "lose" a day. If you depart on a Friday, you'll arrive on a Saturday, completely skipping the rest of Friday.
Fun Facts About Time
The Country with the Most Time Zones
It's not Russia or the USA—it's France! Including its overseas territories, France uses 12 different time zones.
A Wobbly Date Line
In 1995, the nation of Kiribati shifted the IDL eastward to encompass all of its islands, effectively jumping its eastern islands ahead by 24 hours.
Time Moves Slower for You
Due to Einstein's theory of relativity, time passes slightly slower for objects closer to a large gravitational mass. Your feet are technically aging slower than your head.
The "Leap Second"
Occasionally, a "leap second" is added to UTC to keep our clocks in sync with the Earth's slowing rotation. This has happened 27 times since 1972.
Frequently Asked Questions
What is the difference between GMT and UTC?
Greenwich Mean Time (GMT) is a time zone, while Coordinated Universal Time (UTC) is a time standard. For most practical purposes, they are the same. UTC is the more modern, scientific standard used to regulate clocks worldwide.
Why isn't the International Date Line a straight line?
The IDL zigs and zags to avoid cutting through countries or island groups. This prevents situations where one part of a country would be on a different calendar day from the other.
How does Daylight Saving Time (DST) work?
DST is the practice of setting clocks forward by one hour during warmer months to make better use of natural daylight in the evenings. The clocks on this page automatically account for DST changes in their respective locations.