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Decimal time is the representation of the time of day using units which are decimally related. This term is often used specifically to refer to the time system used in France for a few years beginning in 1792 during the French Revolution, which divided the day into 10 decimal hours, each decimal hour into 100 decimal minutes and each decimal minute into 100 decimal seconds (100000 decimal seconds per day), as opposed to the more familiar UTC time standard, which divides the day into 24 hours, each hour into 60 minutes and each minute into 60 seconds (86400 SI seconds per day).
The decimal numeral system is the standard system for denoting integer and non-integer numbers. It is the extension to non-integer numbers of the Hindu–Arabic numeral system. The way of denoting numbers in the decimal system is often referred to as decimal notation.
The French Revolution was a period of far-reaching social and political upheaval in France and its colonies beginning in 1789. The Revolution overthrew the monarchy, established a republic, catalyzed violent periods of political turmoil, and finally culminated in a dictatorship under Napoleon who brought many of its principles to areas he conquered in Western Europe and beyond. Inspired by liberal and radical ideas, the Revolution profoundly altered the course of modern history, triggering the global decline of absolute monarchies while replacing them with republics and liberal democracies. Through the Revolutionary Wars, it unleashed a wave of global conflicts that extended from the Caribbean to the Middle East. Historians widely regard the Revolution as one of the most important events in human history.
A time standard is a specification for measuring time: either the rate at which time passes; or points in time; or both. In modern times, several time specifications have been officially recognized as standards, where formerly they were matters of custom and practice. An example of a kind of time standard can be a time scale, specifying a method for measuring divisions of time. A standard for civil time can specify both time intervals and time-of-day.
The main advantage of a decimal time system is that, since the base used to divide the time is the same as the one used to represent it, the whole time representation can be handled as a single string. Therefore, it becomes simpler to interpret a timestamp and to perform conversions. For instance, 1:23:00 is 1 decimal hour and 23 decimal minutes, or 1.23 hours, or 123 minutes; 3 hours is 300 minutes or 30,000 seconds. This property also makes it straightforward to represent a timestamp as a fractional day, so that 2019-10-25.534 can be interpreted as five decimal hours and 34 decimal minutes after the start of that day, or 0.534 (53.4%) through that day. It also adjusts well to digital time representation using epochs, in that the internal time representation can be used directly both for computation and for user-facing display.
In digital numeral systems, the radix or base is the number of unique digits, including the digit zero, used to represent numbers in a positional numeral system. For example, for the decimal/denary system the radix is ten, because it uses the ten digits from 0 through 9.
In computing, an epoch is a date and time from which a computer measures system time. Most computer systems determine time as a number representing the seconds removed from particular arbitrary date and time. For instance, Unix and POSIX measure time as the number of seconds that have passed since 1 January 1970 00:00:00 UT, a point in time known as the Unix epoch. The NT time epoch on Windows NT and later refers to the Windows NT system time in (10^-7)s intervals from 0h 1 January 1601.
Decimal time was used in China throughout most of its history alongside duodecimal time. The midnight-to-midnight day was divided both into 12 double hours (traditional Chinese : 時辰 ; simplified Chinese : 时辰 ; pinyin :shí chén) and also into 10 shi / 100 ke (Chinese : 刻 ; pinyin :kè) by the 1st millennium BC. Other numbers of ke per day were used during three short periods: 120 ke from 5–3 BC, 96 ke from 507–544 CE, and 108 ke from 544–565. Several of the roughly 50 Chinese calendars also divided each ke into 100 fen, although others divided each ke into 60 fen. In 1280, the Shoushi (Season Granting) calendar further subdivided each fen into 100 miao, creating a complete decimal time system of 100 ke, 100 fen and 100 miao. Chinese decimal time ceased to be used in 1645 when the Shixian (Constant Conformity) calendar, based on European astronomy and brought to China by the Jesuits, adopted 96 ke per day alongside 12 double hours, making each ke exactly one-quarter hour.
The duodecimal system is a positional notation numeral system using twelve as its base. The number twelve is instead written as "10" in duodecimal, whereas the digit string "12" means "1 dozen and 2 units". Similarly, in duodecimal "100" means "1 gross", "1000" means "1 great gross", and "0.1" means "1 twelfth".
Traditional Chinese characters are Chinese characters in any character set that does not contain newly created characters or character substitutions performed after 1946. They are most commonly the characters in the standardized character sets of Taiwan, of Hong Kong and Macau. The modern shapes of traditional Chinese characters first appeared with the emergence of the clerical script during the Han dynasty and have been more or less stable since the 5th century.
Simplified Chinese characters are standardized Chinese characters prescribed in the Table of General Standard Chinese Characters for use in mainland China. Along with traditional Chinese characters, they are one of the two standard character sets of the contemporary Chinese written language. The government of the People's Republic of China in mainland China has promoted them for use in printing since the 1950s and 1960s to encourage literacy. They are officially used in the People's Republic of China, Malaysia and Singapore.
In 1754, Jean le Rond d'Alembert wrote in the Encyclopédie :
Jean-Baptiste le Rond d'Alembert was a French mathematician, mechanician, physicist, philosopher, and music theorist. Until 1759 he was co-editor with Denis Diderot of the Encyclopédie. D'Alembert's formula for obtaining solutions to the wave equation is named after him. The wave equation is sometimes referred to as d'Alembert's equation.
Encyclopédie, ou dictionnaire raisonné des sciences, des arts et des métiers, better known as Encyclopédie, was a general encyclopedia published in France between 1751 and 1772, with later supplements, revised editions, and translations. It had many writers, known as the Encyclopédistes. It was edited by Denis Diderot and, until 1759, co-edited by Jean le Rond d'Alembert.
In 1788, Claude Boniface Collignon proposed dividing the day into 10 hours or 1000 minutes, each new hour into 100 minutes, each new minute into 1000 seconds, and each new second into 1000 tierces (Latin for "third"). The distance the twilight zone travels in one such tierce at the equator, which would be one-billionth of the circumference of the earth, would be a new unit of length, provisionally called a half-handbreadth, equal to four modern centimetres. Further, the new tierce would be divided into 1000 quatierces, which he called "microscopic points of time". He also suggested a week of 10 days and dividing the year into 10 "solar months".
Claude Boniface Collignon was a French attorney who contributed to scientific and social reforms in the time of the French Revolution. He was a member of several European academies of sciences, though not the French Academy of Sciences. In 1788 he proposed the introduction of decimal time. In 1790, perhaps disappointed that the French government had not immediately rewarded him for the plan, he sent his book to George Washington, and proposed to introduce his system in the US.
A terminator or twilight zone is a moving line that divides the daylit side and the dark night side of a planetary body. A terminator is defined as the locus of points on a planet or moon where the line through its parent star is tangent. An observer on the terminator of such an orbiting body with an atmosphere would experience twilight due to light scattering by particles in the gaseous layer.
The equator of a rotating spheroid is the parallel at which latitude is defined to be 0°. It is the imaginary line on the spheroid, equidistant from its poles, dividing it into northern and southern hemispheres. In other words, it is the intersection of the spheroid with the plane perpendicular to its axis of rotation and midway between its geographical poles.
Decimal time was officially introduced during the French Revolution. Jean-Charles de Borda made a proposal for decimal time on November 5, 1792. The National Convention issued a decree on 5 October 1793:
Jean-Charles, chevalier de Borda was a French mathematician, physicist, and sailor.
The National Convention was the first government of the French Revolution, following the two-year National Constituent Assembly and the one-year Legislative Assembly. Created after the great insurrection of 10 August 1792, it was the first French government organized as a republic, abandoning the monarchy altogether. The Convention sat as a single-chamber assembly from 20 September 1792 to 26 October 1795.
These parts were named on 24 November 1793 (4 Frimaire of the Year II). The primary divisions were called hours, and they added:
Thus, midnight was called either dix heures ("ten hours") or zero heures, noon was called cinq heures, etc. Units were either written out or abbreviated, such as 8 h. 72 m. Sometimes in official records, decimal hours were divided into tenths, or décimes, instead of minutes (e.g., 8.7 h.). Although clocks and watches were produced with faces showing both standard time with numbers 1–24 and decimal time with numbers 1–10, decimal time never caught on; it was not officially used until the beginning of the Republican year III, 22 September 1794, and mandatory use was suspended 7 April 1795 (18 Germinal of the Year III), in the same law which introduced the original metric system. Thus, although decimal time is sometimes referred to as metric time, the metric system at first had no time unit, and later versions of the metric system used the second, equal to 1/86400 day, as the metric time unit. In spite of this, decimal time was used in many cities, including Marseille and Toulouse, where a decimal clock with just an hour hand was on the front of the Capitole for five years. On the Palace of the Tuileries in Paris, two of the four clock faces displayed decimal time until at least 1801. The mathematician and astronomer Pierre-Simon Laplace had a decimal watch made for him, and used decimal time in his work, in the form of fractional days.
Decimal time was part of a larger attempt at decimalisation in revolutionary France (which also included decimalisation of currency and metrication) and was introduced as part of the French Republican Calendar, which, in addition to decimally dividing the day, divided the month into three décades of 10 days each; this calendar was abolished at the end of 1805. The start of each year was determined according to the day of the autumnal equinox, in relation to true or apparent solar time at the Paris Observatory. Decimal time would also have been reckoned according to apparent solar time, depending on the location it was observed, as was already the practice generally for the setting of clocks. 23:28:23 GMT is 9h 84m 54s decimal time in Paris.
At the International Meridian Conference of 1884, the following resolution was proposed by the French delegation and passed nem con (with 3 abstentions):
In the 1890s, Joseph Charles François de Rey-Pailhade, president of the Toulouse Geographical Society, proposed dividing the day into 100 parts, called cés, equal to 14.4 standard minutes, and each divided into 10 decicés, 100 centicés, etc. The Toulouse Chamber of Commerce adopted a resolution supporting his proposal in April 1897. Although widely published, the proposal received little backing.
The French made another attempt at the decimalization of time in 1897, when the Commission de décimalisation du temps was created by the Bureau des Longitudes, with the mathematician Henri Poincaré as secretary. The commission adopted a compromise, originally proposed by Henri de Sarrauton of the Oran Geographical Society, of retaining the 24-hour day, but dividing each hour into 100 decimal minutes, and each minute into 100 seconds. The plan did not gain acceptance and was abandoned in 1900.
On 23 October 1998, the Swiss watch company Swatch introduced a decimal time called Internet Time, which divides the day into 1,000 decimal minutes (Swatch called them .beats), (each 86.4 seconds in standard time) counted from 000–999, with @000 being midnight and @500 being noon standard time in Switzerland, which is Central European Time (one hour ahead of Universal Time). A line painted on Swatch headquarters in the Swiss city of Biel (now Biel/Bienne) was declared to mark the Biel Meridian, and Central European Time was relabelled as "Biel Meantime" (BMT), even though it does not correspond to actual local mean time in Biel.
There are exactly 86,400 standard seconds (see SI for the current definition of the standard second) in a standard day, but in the French decimal time system there were 100,000 decimal seconds in the day, so the decimal second was shorter than its counterpart.
Another common type of decimal time is decimal hours. In 1896, Henri de Sarrauton of the Oran Geographical Society proposed dividing the 24 hours of the day each into 100 decimal minutes, and each minute into 100 decimal seconds.Although endorsed by the Bureau des Longitudes, this proposal failed, but using decimal fractions of an hour to represent the time of day instead of minutes has become common.
Decimal hours are frequently used in accounting for payrolls and hourly billing. Time clocks typically record the time of day in tenths or hundredths of an hour. For instance, 08:30 would be recorded as 08.50. This is intended to make accounting easier by eliminating the need to convert between minutes and hours.
For aviation purposes, where it is common to add times in an already complicated environment, time tracking is simplified by recording decimal fractions of hours. For instance, instead of adding 1:36 to 2:36, getting 3:72 and converting it to 4:12, one would add 1.6 to 2.6 and get 4.2 hours.
The time of day is sometimes represented as a decimal fraction of a day in science and computers. Standard 24-hour time is converted into a fractional day by dividing the number of hours elapsed since midnight by 24 to make a decimal fraction. Thus, midnight is 0.0 day, noon is 0.5 d, etc., which can be added to any type of date, including (all of which refer to the same moment):
As many decimal places may be used as required for precision, so 0.5 d = 0.500000 d. Fractional days are often calculated in UTC or TT, although Julian Dates use pre-1925 astronomical date/time (each date began at noon = ".0") and Microsoft Excel uses the local time zone of the computer. Using fractional days reduces the number of units in time calculations from four (days, hours, minutes, seconds) to just one (days).
Fractional days are often used by astronomers to record observations, and were expressed in relation to Paris Mean Time by the 18th century French mathematician and astronomer Pierre-Simon Laplace, as in these examples:
... et la distance périhélie, égale à 1,053095 ; ce qui a donné pour l'instant du passage au périhélie, sept.29j,10239, temps moyen compté de minuit à Paris. Les valeurs précédentes de a, b, h, l, relatives à trois observations, ont donné la distance périhélie égale à 1,053650; et pour l'instant du passage, sept.29j,04587; ce qui diffère peu des résultats fondés sur cinq observations.— Pierre-Simon Laplace, Traité de Mécanique Céleste
Fractional days have been used by astronomers ever since. For instance, the 19th century British astronomer John Herschel gave these examples:
Between Greenwich noon of the 22d and 23d of March, 1829, the 1828th equinoctial year terminates, and the 1829th commences. This happens at 0d·286003, or at 6h 51m 50s·66 Greenwich Mean Time ... For example, at 12h 0m 0s Greenwich Mean Time, or 0d·500000...— John Herschel, Outlines of Astronomy
Fractional days are commonly used to express epochs of orbital elements. The decimal fraction is usually added to the calendar date or Julian day for natural objects, or to the ordinal date for artificial satellites in two-line elements.
The second is the International System of Units (SI) unit of time duration. It is also the standard single-unit time representation in many programming languages, most notably C, and part of UNIX/POSIX standards used by Linux, Mac OS X, etc.; to convert fractional days to fractional seconds, multiply the number by 86400. Fractional seconds are represented as milliseconds (ms), microseconds (μs) or nanoseconds (ns). Absolute times are usually represented relative to 1 January 1970, at midnight. Other systems may use a different zero point (like Unix time).
In principle, time spans greater than one second are given in units such as kiloseconds (ks), myriasecond (mys), megaseconds (Ms), gigaseconds (Gs), and so on. (The myriasecond is based on the myria- prefix, which represented a multiple of 10000 but was made obsolete in the mid-20th century.) Occasionally, these units can be found in technical literature, but traditional units like minutes, hours, days and years are much more common, and are accepted for use with SI.
It is possible to specify the time of day as the number of kiloseconds or myriaseconds elapsed since midnight. Thus, instead of saying 3:45 p.m. one could say (time of day) 56.7 ks. There are exactly 86.4 ks or 8.64 mys in one day. However, this nomenclature is rarely used in practice.
Scientists often record (rather than observe) time as decimals. For example, decimal days divides the day into 10 equal parts, and decimal years divides the year into 10 equal parts. Decimals are easier to plot than both (a) minutes and seconds, which uses the Sexagesimal numbering system, (b) hours, months and days, which has irregular month lengths. In astronomy, the so-called Julian day uses decimal days centered on noon.
Since there are 60 seconds in a minute, a tenth part represents 60/10 = 6 seconds.
Since there are 60 minutes in an hour, a tenth part represents 60/10 = 6 minutes.
Since there are 24 hours in a day, a tenth part represents 24/10 = 2.4 hours (2 hours and 24 minutes).
|Hours/minutes||2h 24m||4h 48m||7h 12m||9h 36m||12h||14h 24m||16h 48m||19h 12m||21h 36m||24h|
Since there are about 365 days in a year, there are about 365/10 = 36.5 days in a tenth of a year. Hence the year 2000.5 represents the day 2 July 2000.More exactly, a Julian year is exactly 365.25 days long, so a tenth of the year is 36.525 days (36 days, 12 hours, 36 minutes).
These values, based on the Julian year, are most likely to be those used in astronomy and related sciences. A Gregorian year, which takes into account the 100/400 leap year rules of the Gregorian calendar, is 365.2425 days (the average length of a year over a 400-year cycle), resulting in 0.1 years being a period of 36.52425 days (3155695.2 seconds; 36 days, 12 hours, 34 minutes, 55.2 seconds).
Numerous individuals have proposed variations of decimal time, dividing the day into different numbers of units and subunits with different names. Most are based upon fractional days, so that one decimal time format may be easily converted into another, such that all the following are equivalent:
Some decimal time proposals are based upon alternate units of metric time. The difference between metric time and decimal time is that metric time defines units for measuring time interval, as measured with a stopwatch, and decimal time defines the time of day, as measured by a clock. Just as standard time uses the metric time unit of the second as its basis, proposed decimal time scales may use alternative metric units.
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A day is approximately the period of time during which the Earth completes one rotation around its axis. A solar day is the length of time which elapses between the Sun reaching its highest point in the sky two consecutive times.
The French Republican calendar, also commonly called the French Revolutionary calendar, was a calendar created and implemented during the French Revolution, and used by the French government for about 12 years from late 1793 to 1805, and for 18 days by the Paris Commune in 1871. The revolutionary system was designed in part to remove all religious and royalist influences from the calendar, and was part of a larger attempt at decimalisation in France. It was used in government records in France and other areas under French rule, including Belgium, Luxembourg, and parts of the Netherlands, Germany, Switzerland, Malta, and Italy.
An hour is a unit of time conventionally reckoned as 1⁄24 of a day and scientifically reckoned as 3,599–3,601 seconds, depending on conditions.
ISO 8601Data elements and interchange formats – Information interchange – Representation of dates and times is an international standard covering the exchange of date- and time-related data. It was issued by the International Organization for Standardization (ISO) and was first published in 1988. The purpose of this standard is to provide an unambiguous and well-defined method of representing dates and times, so as to avoid misinterpretation of numeric representations of dates and times, particularly when data are transferred between countries with different conventions for writing numeric dates and times.
The minute is a unit of time usually equal to 1⁄60 of an hour, or 60 seconds. In the UTC time standard, a minute on rare occasions has 61 seconds, a consequence of leap seconds. Although not an SI unit, the minute is accepted for use with SI units. The SI symbol for minute or minutes is min. The prime symbol is also sometimes used informally to denote minutes of time.
The second is the base unit of time in the International System of Units (SI), commonly understood and historically defined as 1⁄86400 of a day – this factor derived from the division of the day first into 24 hours, then to 60 minutes and finally to 60 seconds each. Analog clocks and watches often have sixty tick marks on their faces, representing seconds, and a "second hand" to mark the passage of time in seconds. Digital clocks and watches often have a two-digit seconds counter. The second is also part of several other units of measurement like meters per second for velocity, meters per second per second for acceleration, and per second for frequency.
Metric time is the measure of time intervals using the metric system. The modern SI system defines the second as the base unit of time, and forms multiples and submultiples with metric prefixes such as kiloseconds and milliseconds. Other units of time: minute, hour, and day, are accepted for use with SI, but are not part of it. Metric time is a measure of time intervals, while decimal time is a means of recording time of day.
Sexagesimal is a numeral system with sixty as its base. It originated with the ancient Sumerians in the 3rd millennium BC, was passed down to the ancient Babylonians, and is still used—in a modified form—for measuring time, angles, and geographic coordinates.
An order of magnitude of time is (usually) a decimal prefix or decimal order-of-magnitude quantity together with a base unit of time, like a microsecond or a million years. In some cases, the order of magnitude may be implied, like a "second" or "year". In other cases, the quantity name implies the base unit, like "century". In most cases, the base unit is seconds or years. Prefixes are not usually used with a base unit of years, so we say "a million years", not "a megayear". Clock time and calendar time have duodecimal or sexagesimal orders of magnitude rather than decimal, i.e. a year is 12 months, and a minute is 60 seconds.
The 24-hour clock is the convention of time keeping in which the day runs from midnight to midnight and is divided into 24 hours, indicated by the hours passed since midnight, from 0 to 23. This system is the most commonly used time notation in the world today, and is used by international standard ISO 8601.
WWV is a shortwave radio station, located near Fort Collins, Colorado. It is best known for its continuous time signal broadcasts begun in 1945, and is also used to establish official United States government frequency standards, with transmitters operating on 2.5, 5, 10, 15, and 20 MHz. WWV is operated by U.S. National Institute of Standards and Technology (NIST), under the oversight of its Time and Frequency Division, which is part of NIST's Physical Measurement Laboratory based in Gaithersburg, Maryland.
Swatch Internet Time is a decimal time concept introduced in 1998 by the Swatch corporation as part of their marketing campaign for their line of "Beat" watches.
A clock face, or dial, is the part of an analog clock that displays the time through the use of a fixed-numbered dial or dials and moving hands. In its most basic form, recognized throughout the world, the periphery of the dial is numbered 1 through 12 indicating the hours in a 12-hour cycle, and a short hour hand makes two revolutions in a day. A long minute hand makes one revolution every hour. The face may also include a second hand, which makes one revolution per minute. The term is less commonly used for the time display on digital clocks and watches.
A degree, usually denoted by °, is a measurement of a plane angle, defined so that a full rotation is 360 degrees.
Hexadecimal time is the representation of the time of day as a hexadecimal number in the interval (0,1).
France has a unique history of units of measurement due to the radical decision to invent and adopt the metric system after the French Revolution.
The traditional Chinese time systems refers to the time standards for divisions of the day used in China until the introduction of the Shixian calendar in 1628 at the beginning of the Qing dynasty.
New Earth Time is an alternative naming system for measuring the time of day. In NET the day is split into 360 NET degrees, each NET degree is split into 60 NET minutes and each NET minute is split into 60 NET seconds. One NET degree is therefore equivalent to four standard minutes, and one standard hour is equivalent to 15 NET degrees.
Overall equipment effectiveness (OEE) is a measure of how well a manufacturing operation is utilized compared to its full potential, during the periods when it is scheduled to run. it identifies the percentage of manufacturing time that is truly productive. An OEE of 100% means that only good parts are produced, at the maximum speed, and without interruption.