60 Fun Facts About Time

Since 1967 the second has been defined by the radiation frequency of an atom of which element?

The definition counts 9,192,631,770 periods of caesium-133 radiation. Optical clocks based on strontium and aluminium ions are now more precise, so the definition may change again.

The name for the 60th division of a minute comes from the Latin pars minuta secunda, meaning what?

The minute was the pars minuta prima, the first small division of the hour into 60 parts; dividing again by 60 gave the second small part.

How many leap seconds have been added to UTC since the system began in 1972?

The most recent was on 31 December 2016, and UTC now trails International Atomic Time by 37 seconds. Metrologists voted in 2022 to stop adding them by 2035.

Which year is the longest on record, at 31,622,402 seconds, because it had 366 days and two leap seconds?

1972 was the first year of leap seconds and got two of them, in June and December, on top of being a leap year.

Why is Coordinated Universal Time abbreviated UTC rather than CUT?

English speakers wanted CUT and French speakers TUC; UTC matched the existing pattern of UT0, UT1 and UT2 and satisfied nobody equally, which is how it won.

In which city did the 1884 International Meridian Conference choose Greenwich as prime meridian?

Forty-one delegates from 25 nations attended at the invitation of the US president. Greenwich, Paris, Berlin and Washington observatories were the serious candidates.

Which country's Line Islands sit at UTC+14, the most advanced time zone on Earth?

UTC+13 and UTC+14 did not exist until Kiribati moved its eastern half across the Date Line at the end of 1994 so the whole country shared one date.

Which country keeps its clocks 5 hours 45 minutes ahead of UTC?

The offset approximates Kathmandu mean time. Nepal was the last country to settle its standard offset, nudging its clocks forward 15 minutes in 1986.

Which country spans five geographical time zones yet officially observes just one, set to its capital?

Everything runs on UTC+8, Beijing time, so in the far west the sun can rise after 9 a.m. by the clock. Five zones were proposed in 1918 but never fully used.

Which company was the first to standardise its timetable on Greenwich Mean Time, in November 1840?

Before 'railway time', towns kept their own local mean time, and Bristol ran about ten minutes behind London. Britain did not legislate a single standard time until 1880.

In 1883, US and Canadian railroads switched to standard time on a telegraph signal from an observatory in which city?

The signal came from the Allegheny Observatory at exactly noon on the 90th meridian. Newspapers called it the day of two noons.

Scottish-born engineer Sir Sandford Fleming proposed worldwide time zones in the 1870s while working in which country?

Fleming also engineered much of the Canadian Pacific Railway. His 24-zone lettered scheme was never adopted directly, but the idea of hourly zones was.

Strictly speaking, 'Big Ben' is the nickname of what?

The name spread to the tower by extension. It probably honours Sir Benjamin Hall, the tall commissioner of works who oversaw the bell's installation.

Clockmakers fine-tune the Great Clock of Westminster by adding or removing what from its pendulum?

Each pre-decimal penny changes the clock's rate by 0.4 seconds a day. The clock has been famous for its reliability since 1859.

In 2012 the Palace of Westminster's clock tower was officially renamed in honour of whom?

The tower became the Elizabeth Tower for the Diamond Jubilee, mirroring the renaming of the palace's west tower for Queen Victoria's jubilee. Before that it was simply the Clock Tower.

The 13.5-ton bell nicknamed Big Ben was cast by which East London firm?

The same East London foundry cast Philadelphia's Liberty Bell. It closed in 2017 after more than 400 years of operation.

Who invented the pendulum clock in 1656?

Huygens was inspired by Galileo's work on pendulums and had clockmaker Salomon Coster build the first examples. Nothing beat it until quartz in the 1930s.

The first quartz clock was described and built in October 1927 at which organisation?

Warren Marrison and Joseph Horton's clock used a crystal vibrating at 50,000 cycles per second. Quartz wristwatches took another four decades.

Which company sold the world's first commercial quartz wristwatch, the Astron, in December 1969?

The Astron 35SQ is now an IEEE Milestone. Swiss makers had shown a rival prototype, the Beta 1, in 1967 but were beaten to market.

Which physicist built the first practical atomic clock at Britain's National Physical Laboratory in 1955?

Essen worked with Jack Parry. Rabi had built the underlying atomic-beam resonance equipment in the 1930s, and an ammonia prototype ran in 1949.

In 1971 Hafele and Keating tested relativity by flying four atomic clocks around the world aboard what?

They flew eastward, then westward, and compared the travelling clocks with ones left at the US Naval Observatory. The tiny differences matched relativity's predictions.

Unix time counts seconds elapsed since midnight UTC at the start of which date?

That moment is the Unix epoch. Systems storing it as a signed 32-bit number run out of room in January 2038.

The Doomsday Clock's farthest-ever setting from midnight came in 1991. How many minutes was it?

The clock started at seven minutes to midnight in 1947, at the dawn of the Cold War, and by 2026 stood at 85 seconds, its closest ever.

Which publication maintains the Doomsday Clock?

The clock first appeared on the June 1947 cover, drawn by artist Martyl Langsdorf, whose husband had worked on the Manhattan Project.

Time magazine was first published in New York in 1923 by Henry Luce and which co-founder?

Hadden and Luce were Yale classmates. Hadden died in 1929, leaving Luce to build the Time Inc. empire that later included Life and Fortune.

Under the decimal time system of the French Revolution, how many hours were in a day?

Each decimal hour had 100 minutes and each minute 100 seconds, so a day was 100,000 decimal seconds. Midnight was called 'ten hours'.

Swatch Internet Time, launched in 1998, divides the day into 1,000 equal units called what?

Each unit lasts 86.4 seconds and there are no time zones: everyone counts from midnight in Biel, Switzerland, on what Swatch called Biel Mean Time.

The base-60 counting system behind 60 minutes and 60 seconds originated with which ancient people?

It passed to the Babylonians and survives in angles and coordinates too. Ptolemy's Almagest used base 60 for fractions in the second century AD.

Which ancient civilisation divided the night into 12 parts, leading to our 24-hour day?

They watched twelve constellations rise through the night. These were seasonal hours, shorter in summer and longer in winter, not the fixed hours we use now.

The Greek word clepsydra, used for a clock driven by dripping liquid, literally means what?

From kleptein, to steal, and hydor, water. Greek and Roman versions gained gearing, feedback systems and even automata.

The earliest documented hourglass appears in a 1338 fresco, the Allegory of Good Government, by which painter?

There is no record of hourglasses in Europe before the late Middle Ages. A 1345 receipt for twelve 'glass horologes' for an English royal ship is the first firm marine reference.

How many hourglasses from Barcelona were listed in the inventory for Magellan's voyage around the world?

Sand glasses were the standard way to time watches at sea until John Harrison's chronometers in the 18th century made something far steadier possible.

Cuckoo clocks were popularised and exported to the world from which region of Germany?

The earliest known description of a cuckoo clock was written in Augsburg in 1629, decades before Black Forest clockmaking existed, so its true birthplace is murky.

The first telephone speaking clock service was launched on 14 February 1933 in which country?

It was run with the Paris Observatory. Britain's followed in 1936, and its voice service was known for years by the dialling code TIM.

The Times Square ball has dropped every New Year's Eve since 1907 except for two years. Which two?

Wartime blackout rules kept the lights off; crowds gathered anyway for a minute of silence and chimes. New York Times owner Adolph Ochs started the tradition.

Roughly how much did the original 1907 Times Square ball, made of iron and wood, weigh?

It was five feet across, built by sign maker Artkraft Strauss. Today's version is covered in more than 5,000 Waterford Crystal panels.

The time ball at the Royal Observatory, Greenwich, has dropped every day since 1833 at what hour?

Astronomer Royal John Pond installed it so ships on the Thames could set their chronometers. The first modern time ball was at Portsmouth in 1829.

Which city's famous astronomical clock, the Orloj, was first recorded in 1410?

It was made by horologist Mikuláš of Kadaň and mathematician Jan Šindel and still runs. The legend that its maker Hanuš was blinded to stop him copying it is a later invention.

Which billionaire gave $42 million to build the 10,000-year Clock of the Long Now inside a Texas mountain?

Danny Hillis conceived it in 1989. Its prototype chimed twice at midnight as its date wheel turned from 01999 to 02000.

On average, how long does the body take to fully re-set its internal clock after crossing time zones?

Morning light advances the body clock, which helps after flying east; evening light delays it, which helps after flying west.

The word 'circadian', describing the body's roughly 24-hour cycles, comes from Latin words meaning what?

Circa plus dies. The cues that reset the cycle, like light and temperature, are called zeitgebers, German for 'time givers'.

Hall, Rosbash and Young won the 2017 Nobel for uncovering the body-clock genes of which organism?

The key gene, period, sits on the fruit fly's X chromosome. Losing it stops the fly's daily rhythm entirely.

Louis Cartier made a 1904 wristwatch for Alberto Santos-Dumont so he could check the time while doing what?

A pocket watch was hopeless with both hands on the controls. Cartier still sells a Santos-Dumont line more than a century later.

The first Swiss wristwatch, made by Patek Philippe in 1868, was for a countess from which country?

For decades wristwatches were seen as women's jewellery; men carried pocket watches until soldiers and aviators made the wrist practical.

John Harrison's sea watch H4 was trialled in 1761 aboard HMS Deptford on a voyage to which island?

Parliament had offered up to £20,000 under the 1714 Longitude Act after the 1707 Scilly naval disaster. Harrison never received the full sum.

Which Pacific nation deleted Friday 30 December 2011 to jump west of the Date Line?

The move put the country on the same side of the line as its trading partners Australia and New Zealand. Tokelau made the same jump on the same night.

Which Asian country ran a day behind its neighbours until 1844 because it was administered from Mexico?

As part of New Spain its main link was the galleon route to Acapulco, so it kept American dates from Magellan's arrival in 1521 until 1844.

When Alaska switched calendars and crossed the Date Line in 1867, Saturday 7 October locally became what?

Russia still used the Julian calendar, so eleven days were added, while moving east across the Date Line took a day away. Alaska Day is celebrated on 18 October.

The first clock recorded as striking regularly on the hour was set up in 1336 in which city?

It used a verge and foliot escapement, invented around 1275. Early mechanical clocks drifted so much they were routinely reset against a sundial.

The a.m. in clock times abbreviates the Latin ante meridiem, which means what?

P.m. is post meridiem, after midday. Many countries speak in 12-hour time but write timetables and official documents in 24-hour time.

The Y2K bug happened because many programs stored the year using how many digits?

With memory costing up to $100 a kilobyte in 1975, '85' was cheaper than '1985', so 2000 became indistinguishable from 1900. Estimates of the fix ran to $600 billion.

The Westinghouse time capsule buried at the 1939 World's Fair is due to be opened in what year?

A second Westinghouse capsule joined it in 1965 with the same opening date. Oglethorpe University's Crypt of Civilization, sealed in 1940, waits until 8113.

Stonehenge's main axis is aligned to the sunrise on which day of the year?

The same line points to sunset on the winter solstice, and the north-eastern entrance was widened to match it precisely, making the monument a giant seasonal clock.

The shortest meaningful unit of time in physics is named after which physicist?

It is roughly 5.4 × 10⁻⁴⁴ seconds. The smallest interval ever directly measured, in 2010, was still about 12 attoseconds, or 3.7 × 10²⁶ Planck times.

On a sundial, what is the shadow-casting rod or plate called?

Its time-telling edge is the style. Cheap garden sundials often have the gnomon set at the wrong angle for their latitude, so they can never read correctly.

Su Song's water-powered astronomical clock of 1088 had the first known example of what?

The Chinese polymath's tower stood in Kaifeng and drove an armillary sphere. Europe's escapement clocks came almost two centuries later.

The oldest surviving water clock (c. 1400 BC) was used at Karnak under which pharaoh?

Simple outflow bowls existed in Babylon, Egypt and Persia by the 16th century BC. Egyptian versions used grooved notches inside the vessel to mark the hours.

Roughly how far did the Julian calendar drift against the solstices and equinoxes each year?

Pope Gregory XIII's 1582 correction took centuries to be adopted worldwide.

According to the Vedas, how long does each cycle of cosmic creation, destruction and rebirth last?

Many Eastern traditions saw time as cyclical rather than a straight line.

Which 5th-century BC Greek argued that time, motion and change were illusions, inspiring Zeno's paradoxes?

Antiphon the Sophist had called time merely a concept or a measure rather than a reality.