Chronography of Metrology

Page last modified 19/10/2021


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See also Science and Technology for other related timelines.

See also Price-Currencies for historic weights and measures


See below for Measuring Time and Dates


21/1/1962The Meteorological Office started using Centigrade as well as Fahrenheit.

1960, The 11th General Conference on Weights and Measures replaced the physical metre with a definition based on radiation from Krypton-86. In 1983 this was changed again to the distance light travels in a specified time.

1954, The 10th General Conference on Weights and Measures added a fourth basic unit, the Kelvin as unit of temperature (see 1889).

1889, The first General Conference on Weights and Measures established international prototypes for the metre and kilogramme. Together with the second as unit of time, these became the three base units of measurement. See 1954.

1848, William Thompson, Lord Kelvin, established absolute zero as -273 C.

30/3/1791, The metric system of measurements was proposed in France.

1785, Watt devised the �horsepower� as a unit of work.

30/4/1772, The first dial weighing machine was patented by John Clais in London.

1761, The first marine chronometer that was accurate to within half a minute per year was made by Paul Harrison, England.

25/4/1744, Anders Celsius, Swedish astronomer who devised the Centigrade temperature scale in 1742, died.

16/9/1736, The German scientist Gabriel Fahrenheit, who devised a scale of temperature, died.

1720, Fahrenheit invented the mercury thermometer.

27/11/1701, Anders Celsius, Swedish astronomer who devised the Centigrade scale of temperature in 1742, was born in Uppsala.

1700, Fahrenheit invented the alcohol thermometer.

24/5/1686. Gabriel Daniel Fahrenheit, the German physicist who invented the mercury thermometer, was born in Danzig.

1613, Pierre Vernier invented the Vernier Measure, in which a slider is used to increase the accuract of the distance measured by a factior of ten.

1305, The English acre was defined by statute as 4,840 square yards.

1101, In England, King Henry VIII introduced the yard as a measure of length, the length of his arm.

789, Charlemagne introduced the Royal Foot as unit of length and the �Karlspfund� as unit of weight, equivalent to 365g or about 13 oz.

2000 BCE. Mesopotamia possessed a standard system of weights and measures. The Shekel consisted of 129 grains (8.36 g), and the Mina, 60x as large, were in use by 2400 BCE. By 2000 BCE the Mesopotamians also used the log (0.541 litres, or 33 cubic inches), the homer (720 logs), and the cubit and foot. The cubit was about 18 inches, the distance from the elbow to the tip of the middle finger.

3100 BCE, Cunieform writing developed in Mesopotamia; temple records and accounts kept.


Measuring Time and Dates

1969, The first quartz wristwatches went on sale, in Japan.

1967, The 13th General Conference on Weights and Measures changed the definition of a second from 1/86,400 of an average solar day to a number of readiation cycles produced by a Caesium-133 atom.

25/10/1960, The Bulova Accutron tuning fork watch, introduced this day, had a tuning fork that vibrated 360 times per second, 144x as fast as the balance oscillators in other hand wound conventional and electrical watches. It was the most accurate watch to date, keeping time to within 1 minute pre month.

1957, The first battery-powered watches went on sale, in the USA.

1955, The first microwave atomic clock was unveiled at the National Physical Laboratory, Teddington, UK. It was accurate to one second every 300 years. By 2020 atomic clocks were accurate to in second every 300 million years.

1949, The first atomic clock was made.

1935, Dendrochronology, counting tree rings to estimate dates, was developed by AE Douglass,

1928, The first quartz crystal clock was made.

7/7/1923, John Harwood patented the first self-winding wristwatch. Self-winding watches already existed but they were bulky fob-watches. The concept was to use a small swinging weight to wind the timepiece.

21/3/1915, Frederick Winslow Taylor, the inventor of modern scientific time-management, died.

13/10/1884. Greenwich was adopted as the universal time meridian from which world longitude is calculated.

13/3/1884, Standard time zones were established in the USA.

20/3/1856, Frederick Winslow Taylor, the inventor of modern scientific time-management, was born.

1820, The British Royal Navy ceased to use half-hour sandglasses to keep the time.

24/3/1776, John Harrison, watchmaker and inventor of the chronometer, died in London.

3/9/1752. The date changed this day to 14/9/1752 with the introduction of the Gregorian Calendar. See 5/4/1753. See also 5/10/1582, start of Gregorian calendar. Crowds of people protested, believing their lives had been �shortened� by 11 days (days 3-13 September 1752 inclusive did not exist).The old calendar had a leap year every 4th year, and therefore was 365.25 days long.However the calendar had now got out of step with the real year.The new calendar omitted leap years every century, unless the year was divisible by 400. See 1/1/45 BCE.

1/1/1752, Officially the first �new year� to fall on 1st January; previously the new year had begun on 25th March.

8/6/1695, Christiaan Huygens, the Dutch scientist who invented the pendulum clock, died (born 1629).

1680, Clocks began to have minute hands. By the mid 1700s second hands were also in use.

12/1656, The pendulum clock was invented by Huygens.

1/1/1622, In the Gregorian Calendar, January 1 was declared the first day of the year, instead of March 25.

1509, The earliest watches were invented by Peter Henlein of Germany; they were named �Nuremberg Eggs�.

1386, The first public clock in England was installed, at Salisbury Cathedral.

1353, The first known public clock was erected, in Milan, Italy.

1350, The oldest known alarm clock was made in Wurzburg, Germany.

1335, The first clock to strike the hours was made in Milan, Italy.

1325, The first clock with a dial was installed at Norwich Cathedral, England.

890, Marked candles were used in England to measure time.

159 BCE, The first water clock (clepsydra), in Rome.


The Roman Calendar

1/1/45 BCE, The Julian Calendar, introduced by Julius Caeasar (reigned 63-46 BCE), began. In 46 BCE Caesar reformed the Roman Calendar. Advised by the Alexandrian astronomer Sosigenes, he first added 67 days to the current year, to compensate for the missed intercalary months (see 700 BCE). This year was therefore 445 days long. The Roman year now contained 365 days, with an extra day added every 4 years to make up then then-known solar year of 365.25 days (see 3/9/1752). The month lengths were rearranged to consist of 7 31 days, 4 30 days, and one of 28 or 29 days. Quintilis month was now renamed Julius in Caesar�s honour. However the Roman priests erroneously added the ;eap year every three years, so that in 8 CE Emperor Augustus reformed the calendar again by skipping several leap years to restore the months to their proper place in the solar year. The month Sextilis was then renamed Augustus in his honour. This basically set the calendar as we know it today, with the exception of the Gregorian reforms from 1582 necessary because the solar year in fact fell just short of 365.25 days, making ther true date of Easter hard to calculate.


Julius Caesar introduced the Julian Calendar. The Julian 365-day calendar was based upon the Egyptian calendar, and replaced an earlier 355-day calendar used by the Romans. The Roman year began in March, and the 5th month, Qunitilis, was renamed July after Julius Caesar himself. Augustus then named the 6th month after himself, too. The Calends was the first day of the month, and in longer months of 312 days the Nones were on the 7th and the Ides on the 15th. In shorter months the Ides and Nones fell on the 5th and 13th days. The Romans also used an 8-day week with the days lettered A to H. For a while this co-existed with the 7-day week, based on the Sun, Moon and 5 visible planets. In 321 AD Emperor Constantine ruled that the 7-day week alone was to be used.


700 BCE, The original Roman calendar had ten months, plus around 60 days not included in any month. This calendar began on the Spring Equinox, known as Martius I. The nxt nine months were called Aprilis, Maius, Junius (these first 4 months after Roman gods), then Quintilis, Sextilis, September, October, November and December, after the words for numerals 5 to 10. Then came the days of winter which had no month name or set number of days and could vary in legth to make the entire year come to 360 days. This variation arose because the High Priest in charge of the calendar could add or subtract days from the ten months as he saw fit, for political gain. In 700 BCE Numa Pompilius, 2nd King of Rome, attempted to introduce some consistency by instituting the two months of February and January (Januarius, named afte the god of doors, the start of the year). In 150 BCE the order of these twomonths was reversed.


Pompilius knew that the year was about 365 days long, and that the liunar cycle was 29.5 days; 12 liunar cycles came to 354 days. He decided on 12 months, 4 of 31 days, 7 of 29 days, and one of 28 days, so as to stay as close as possible to the lunar cycles. The Roman calendar now consisted of Martius (31), Aprilis (29), Maius (31), Junius (29), Quintilis (31), Sextilis (29), September (29), October (31), November (29), December (29), February (28) and January (29), totalling 355 days. This fell short of the solar year by 10 days, so every other year a thirteenth month., Mercedinus, 22 or 23 days long, was added coming after Febriary 23 or 24, so years were now 355, 377, or 378 days long. However the High Priest was still in charge of deciding the insertion and length of the extra month, and could still manipulate the calendar for political advantage. The intercalary month could be omitted completely, and in the reign of Julius Caesar, 63-46 BCE, just 5 such months had been added instead of the expected 8. Hence Ceasar�s reforms, see 1/1/44 BCE.


3500 BCE, Earliest sundials (obelisks) in use, in Egypt.


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