The International Space Station Is on a Time Zone

Time zones are tailor-made for Earthlings, as they (roughly) align with the planet’s 24-hour-long day, but what about the people and space missions we’ve sent beyond Earth? For all missions, including those on the International Space Station, NASA uses Coordinated Universal Time (UTC). UTC is similar to Greenwich Mean Time (GMT) — they share the same current time — but with a subtle difference. Whereas GMT is just one of many time zones, UTC is a time standard. UTC is the global time used by scientists, and it’s constantly calibrated using hyperaccurate atomic clocks; scientists will also occasionally add leap seconds to make up for Earth’s rotational irregularities.

There Is a Movement to Abolish Time Zones

Speaking of Coordinated Universal Time, some argue that UTC should be true to its name and become the universal time for all of Earth’s 8 billion inhabitants. Supporters of ditching time zones concede that it would take some adjustment; New Yorkers might eat breakfast at “noon,” while Tokyo would just be starting its day at “midnight” (only those longitudinally aligned with London would escape this fiasco). But, proponents argue, the change would ease confusion in the long run while potentially allowing our bodies to live more closely with our natural circadian rhythms. The transition may not be as hard as you think — the aviation industry, for example, has been using UTC for years, so maybe one day the rest of humanity will make the switch.

Spain Has Been in the “Wrong” Time Zone for 80 Years

World War II saw a lot of time zone switching, and in 1940, Spain’s dictator Francisco Franco moved his country out of Greenwich Mean Time to Central European Time, meaning the nation now shares a time zone with Eastern European countries such as Poland and Hungary. Franco made this seemingly nonsensical change to bring Spain’s time in line with German-occupied Europe during the war. Although Franco died in 1975, Spain remains on Central European Time despite many proposals to ”slow” down to GMT.

Daylight Saving Altered Time Zones Because of World War I

Love it or hate it (and most seem to hate it), daylight saving time was originally a wartime measure. First instituted by Germany in 1916 to conserve energy and provide more daytime working hours, the idea was quickly adopted by the Allied powers in France, Britain, and eventually the U.S. On March 19, 1918, President Woodrow Wilson signed the Standard Time Act into law, establishing daylight saving time as well as the U.S.’s first five time zones. The U.S. operated on daylight saving time for seven months in both 1918 and 1919, but when the war ended in November 1919, Congress repealed the daylight saving portion of the Standard Time Act and states were once again allowed to choose whether they wanted to use DST.

When war raged across Europe a few decades later, the U.S. quickly instituted daylight saving time year round, which earned it the nickname “War Time.” After the war’s end, standard time once again returned, until the 1966 Uniform Time Act finally mandated the use of daylight saving time across the country. Today, there are efforts to make daylight saving time the permanent time throughout the U.S.

For Two Hours Every Day, Three Days Occur at the Same Time

When the Republic of Kiribati, an island nation in the Pacific, formed in 1979, the international date line bisected its country. While the Gilbert Islands were at UTC+12, other islands, the Phoenix and Line Islands, were at UTC-11 and UTC-10 respectively. To fix this, on New Year's Day in 1995, a large bulge of the date line extended eastward to encompass all of the nation’s 33 islands, effectively adding two new time zones, known as UTC+13 and UTC+14.

Although it makes temporal sense for Kiribati to be living in the same day, the change also introduced a strange quirk in which for two hours every day, three days are happening on Earth at the same time. For example, when the Line islands (in UTC+14) tick over to a new day — let’s say Wednesday — non-Kiribati islands westward in UTC-11 (Midway, American Samoa, etc.) are still experiencing late Monday, as they’re 25 hours behind. Two uninhabited UTC−12 territories, Baker Island and Howland Island, are 26 hours behind, which is why the anomaly persists for two hours. Meanwhile, the rest of the world is experiencing all the various hours of Tuesday, and mostly unaware of the strange temporal happenings taking place in the middle of the Pacific.

France Covers More Time Zones Than Any Other Country

Although mainland France is only in one time zone — Central European Time — its overlying territories span 11 other time zones (technically 13, if you include Antarctic claims and summer time zones), the most of any other country in the world. The country’s westernmost territory, Tahiti in the French Polynesian islands, lies in the UTC-10 time zone, while its easternmost time zone is also in the South Pacific but on the other side of the international date line — Wallis & Futuna islands in UTC+12. Although France is a world leader when it comes to time zones, Russia is a close second-place finisher with 11 time zones, most of which lie in mainland Russia (the main exception being the province of Kaliningrad).

Greenwich, London, Was the Logical Choice for the Prime Meridian

When it comes to time, the borough of Greenwich in London, England, is at the center of the world. That’s because Greenwich Mean Time (GMT) has historically been considered universal time. In 1884, Greenwich was chosen as the center of world time for reasons of convenience. First of all, a year earlier, the U.S. had based its national time zones on a meridian that ran through Greenwich. Secondly, in the late 19th century much of the world’s commerce depended on maritime trading, and most sea charts also used the Greenwich meridian as the primary point of reference. As such, this particular meridian, which ran from the North Pole to the South Pole and crossed directly through Greenwich’s Royal Observatory, became the world’s prime meridian. Set to 0 degrees longitude, the prime meridian is the line upon which GMT was established in order to set the standard for world time. In 1967, Coordinated Universal Time (UTC) was introduced as a GMT equivalent and an updated global time standard. At this point, GMT was technically reduced to just a time zone, although it’s still used as a common vernacular to tell the world’s time.

The International Date Line Makes Time Travel Real

In 1884, the International Meridian Conference was held in Washington, D.C., with the goal of choosing a longitudinal equivalent to the equator and standardizing time throughout the world. At the conference, the prime meridian was established as a way to divide the Eastern and Western hemispheres just as the equator divides the Northern and Southern. At the same time, the 26 nations that attended the conference created another invisible line: the international date line (IDL). The IDL was created to demarcate the difference between one calendar day from the next. Set to a 180-degree longitude meridian, the IDL begins at both poles and then zig-zags around the globe, mostly through a remote section of open ocean. Interestingly enough, since the IDL has no lawful status, countries are free to choose the dates they observe. Case in point: In 2011, Samoa decided to change its time zone by crossing the international date line and skipping an entire calendar day, thereby time-traveling into the future. The change was made in order to improve trade relations with Australia and New Zealand, two countries with whom Samoa conducts regular business.

Time Zones Were Invented for the Railroad

Before mechanical clocks were invented, people used sundials to tell the time. “Noon” was considered to be when the sun was at its highest point in the sky, due south. As a result, each town and city had its own version of time even after the introduction of mechanical timepieces. With the invention of the transcontinental railroad, however, the lack of standardized time became problematic. As people left one city and traveled by railroad across the country, watches had to be reset frequently to accommodate the different times at each station. To solve this predicament, the U.S. borrowed the idea of time zones from Sir Sandford Fleming. A Canadian railroad engineer, Fleming had originally come up with the idea of dividing the world into 24 different longitudinally-based time zones, each with an hourly variation. The U.S. adopted this idea nationally, creating four different zones based on degrees of longitude. A year later, England, Scotland, and Wales followed suit, and eventually, the rest of the world did too.

One Size Doesn’t Fit All

When it comes to the geographical size of a country, the number of time zones is nothing but inconsistent. Some of the world’s largest nations have one time zone, while smaller nations have many. For example, even though the width of India is roughly the same distance between Utah and New York, the entire country has a unified time zone of GMT+5:30. Originally, China had five geographical time zones — Zhongyuan, Longshu, Tibet, Kunlun, and Changbai — that were created in 1912. In 1949, however, the Communist party set all five of these time zones to Beijing’s GMT+8. As a result, some Chinese cities keep alternative workday schedules in order to stay aligned with Beijing. Conversely, France, a country with a more diminutive size geographically, has 12 time zones in total, thanks to its 11 overseas territories. And Märket, a tiny island in the Baltic Sea, has two different time zones, as it’s controlled on either side by Sweden and Finland.

Standard Time Isn’t Always On the Hour

Oddly enough, some countries don’t keep their time on the hour, instead choosing to use half or quarter hours to tell universal time. India, for example, is set to GMT+5:30, as is its neighboring country of Sri Lanka. Other countries that also are on the half-hour include Iran (GMT+3:30), Afghanistan (GMT+4:30), and Burma (GMT+6:30). Even more curious, Nepal is a country that runs on the quarter-hour, as its universal time is set to GMT+5:45. If that’s not strange enough, Australia has five time zones, and only some of them are set to the half or quarter-hour on the clock. There’s no universal answer as to why the times are set this way; rather, it’s often a result of the politics of each nation. For example, India’s decision to set time on the half-hour was a compromise that accommodated New Delhi's location between two meridians. Setting the clock at the median hour was a concession that didn’t favor either longitude and presumably offset the fact that the large country runs on a single time zone.