Oct 13, 2026 · 14 min · 9 segments
Sailors had been able to calculate their position at sea for well over a century by the time the world finally agreed on where longitude should start counting from. On October 13, 1884, delegates…
By the late 19th century, the world had steamships, transatlantic telegraph cables, and railroads crossing entire continents in hours instead of weeks.
But it still didn't have a shared answer to a basic question: What time is it right now everywhere at once? This problem has come up before in a couple of our episodes.
It broke down completely once trains and telegraph lines demanded precise shared schedules.
American railroad companies had already started fixing this on their own, carving up the country into unofficial time zones just to stop trains from colliding on shared track.
A shipment could arrive six hours late and still be technically on schedule, depending entirely on whose clock the paperwork referenced.
Insurance claims, banking wires, and trade contracts all operated on definitions of now that shifted depending on which country was doing the counting.
United States President Chester Arthur called for a solution, and in October 1884, delegates from 25 nations gathered in Washington, DC for the International Meridian Conference, tasked with settling one specific question: Where should the world's maps and clocks start counting from? Britain arrived with an advantage nobody could easily argue against.
Over 70% of the world's shipping tonnage already used Greenwich reference charts, not because any treaty required it, but because the British naval charts and almanacs had simply become the most widely trusted and available.
Still, agreeing to formalize what most of the world already did in practice meant every other nation had to publicly concede the point, and that made the negotiations far more political than technical.
By the late 19th century, the world had steamships, transatlantic telegraph cables, and railroads crossing entire continents in hours instead of weeks.
But it still didn't have a shared answer to a basic question: What time is it right now everywhere at once? This problem has come up before in a couple of our episodes.
It broke down completely once trains and telegraph lines demanded precise shared schedules.
American railroad companies had already started fixing this on their own, carving up the country into unofficial time zones just to stop trains from colliding on shared track.
A shipment could arrive six hours late and still be technically on schedule, depending entirely on whose clock the paperwork referenced.
Insurance claims, banking wires, and trade contracts all operated on definitions of now that shifted depending on which country was doing the counting.
United States President Chester Arthur called for a solution, and in October 1884, delegates from 25 nations gathered in Washington, DC for the International Meridian Conference, tasked with settling one specific question: Where should the world's maps and clocks start counting from? Britain arrived with an advantage nobody could easily argue against.
Over 70% of the world's shipping tonnage already used Greenwich reference charts, not because any treaty required it, but because the British naval charts and almanacs had simply become the most widely trusted and available.
Still, agreeing to formalize what most of the world already did in practice meant every other nation had to publicly concede the point, and that made the negotiations far more political than technical.
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