Decimal time

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, 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.... 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.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... 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, 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. 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 2019-08-06.534 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. 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. In 1754, Jean le Rond d'Alembert wrote in the Encyclopédie: 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'. 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: 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. Because of this, astronomers still use decimal time. 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. 12:09:02 GMT is5h12m76sdecimal time in Paris.