On this day in 1879, at a meeting of the Royal Canadian Institute in Toronto, Scottish-Canadian engineer and inventor Sandford Fleming proposed the idea of standard time zones based on a single universal world time. He suggested that standard time zones could be used locally, but would follow a single world time, which he called “Cosmic Time”. The proposal divided the world into twenty-four time zones, each one covering 15 degrees of longitude. All clocks within each zone would be set to the same time as the others but differed by one hour from those in the neighboring zones.

We take time zones for granted today, but for most of human history, time was kept locally, based on how people in each town or city measured the position of the sun. Most humans did not travel beyond their community, and the few who did would takes days or weeks, so it never really made a difference whether one city was hours off from another one.

But the development of rail travel in the late 19th century posed a huge challenge. For the first time in history, people were crossing through multiple towns in the span of hours, leading to the absurd practice of having to continually reset clocks throughout the day.

As the first country to industrialize, Great Britain was the first to deal with this problem on a large scale; in response, it established Greenwich Mean Time, which was the mean solar time on the Prime Meridian at Greenwich, England. (Ironically, this had been developed to resolve the same issue with respect to ocean navigation. Each country had its own prime meridian in its navigational charts to serve as something of a starting point; it usually passed through the country in question, until the navally dominant British developed the Prime Meridian that most others would soon follow.) Clocks in Britain were set to this time irrespective of local solar noon.

Anyway, Fleming’s proposal gave way to a flurry of international discussion about how to address this issue. The British government even forwarded his work to eighteen foreign countries and several scientific bodies to determine a solution. The United States called an “International Meridian Conference” in 1884 that gathered delegates from around the world to set up a universally recognized basis for time. It was announced the Greenwich Mean Time would be used, for the simple reason that by then, two-thirds of all nautical charts and maps already used it as their prime meridian

By 1972, all major countries adopted time zones based on the Greenwich meridian (since 1935, called “Universal Time”). The saga of universal time is yet another example of our species’ move towards a more global and interconnected community.