question: When did we start using small denominations of time (sec, min, hour), and why is it so uniform between countries?
comment: Lets start at the front of the Question. The first clocks only hand the hour hand, you guessed the rest, circa 1600 +or-. {some should fact check the date of the earliest consumer clock, for accuracy}. By the 1700's the two hand clock appears, a bit later on the sweep\[second hand\]. Some clocks came with a calendar wheel, to show the date. The uniformity comes first with the railroads, and later with mass transportation. Most of the mad desire to 'know the time' comes with the advent of the Industrial Revolution, and the 'other revolutions' in progress, thereafter
passages: In certain languages such as Spanish, Portuguese, Dutch, and English the hour is divided into quarters and halves, spoken of relative to the closest hour.
  
  In Czech language quarters and halves always refer to the following hour, e.g. "čtvrt na osm" (quarter on eight) meaning 7:15, "půl osmé" (half of eight) meaning 7:30 and "tři čtvrtě na osm" (three quarters on eight) meaning 7:45.
   Sexagesimal divisions of the day from a calendar based on astronomical observation have existed since the third millennium BC, though they were not seconds as we know them today. Small divisions of time could not be counted back then, so such divisions were figurative. The first timekeepers that could count seconds accurately were pendulum clocks invented in the 17th century. Starting in the 1950s, atomic clocks became better timekeepers than earth's rotation, and they continue to set the standard today.
  
  Section::::Clocks and solar time.
   In Thailand, Laos, and Cambodia, the traditional system of noting hours is the six-hour clock. This reckons each of a day's 24 hours apart from noon as part of a fourth of the day. 7 am was the first hour of the first half of daytime; 1 pm the first hour of the latter half of daytime; 7 pm the first hour of the first half of nighttime; and 1 am the first hour of the latter half of nighttime. This system existed in the Ayutthaya Kingdom, deriving its current phrasing from the practice of publicly announcing the daytime hours with a gong and the nighttime hours with a drum. It was abolished in Laos and Cambodia during their French occupation and is uncommon there now. The Thai system remains in informal use in the form codified in 1901 by King Chulalongkorn.
   Section::::Historical development.:French decimal time.
   In 1267, the medieval scientist Roger Bacon stated the times of full moons as a number of hours, minutes, seconds, thirds, and fourths ("horae", "minuta", "secunda", "tertia", and "quarta") after noon on specified calendar dates. Although a third for of a second remains in some languages, for example Arabic ثالثة, the modern second is further divided decimally.
   Each day in the Republican Calendar was divided into ten hours, each hour into 100 decimal minutes, and each decimal minute into 100 decimal seconds. Thus an hour was 144 conventional minutes (more than twice as long as a conventional hour), a minute was 86.4 conventional seconds (44% longer than a conventional minute), and a second was 0.864 conventional seconds (13.6% shorter than a conventional second).
   Clocks were manufactured to display this decimal time, but it did not catch on. Mandatory use of decimal time was officially suspended 7 April 1795, although some cities continued to use decimal time as late as 1801.
  
  The numbering of years in the Republican Calendar by Roman numerals ran counter to this general decimalization tendency.
  
  Section::::Months.
   During Europe's Middle Ages, the Roman hours continued to be marked on sundials but the more important units of time were the canonical hours of the Orthodox and Catholic Church. During daylight, these followed the pattern set by the three-hour bells of the Roman markets, which were succeeded by the bells of local churches. They rang prime at about 6am, terce at about 9am, sext at noon, nones at about 3pm, and vespers at either 6pm or sunset. Matins and lauds precede these irregularly in the morning hours; compline follows them irregularly before sleep; and the midnight office follows that. Vatican II ordered their reformation for the Catholic Church in 1963, though they continue to be observed in the Orthodox churches.
   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.
   The system of Italian hours can be seen on a number of clocks in Europe, where the dial is numbered from 1 to 24 in either Roman or Arabic numerals. The St Mark's Clock in Venice, and the Orloj in Prague are famous examples. It was also used in Poland and Bohemia until the 17th century.
   Section::::History.:France.
  
  In 1754, Jean le Rond d'Alembert wrote in the "Encyclopédie":
   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.
   Section::::Conversions.
  
  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.
  
  Section::::Decimal hours.
   During the French Revolution in 1793, in connection with its Republican calendar, France attempted to introduce a decimal time system. This had 10 decimal hours in the day, 100 decimal minutes per hour, and 100 decimal seconds per minute. Therefore, the decimal hour was more than twice as long (144 min) as the present hour, the decimal minute was slightly longer than the present minute (86 seconds) and the decimal second was slightly shorter (0.86 sec) than the present second. Clocks were manufactured with this alternate face, usually combined with traditional hour markings. However, it did not catch on, and France discontinued the mandatory use of decimal time on 7 April 1795, although some French cities used decimal time until 1801.
   The earliest mechanical clocks which appeared starting in the 14th century had displays that divided the hour into halves, thirds, quarters and sometimes even 12 parts, but never by 60. In fact, the hour was not commonly understood to be the duration of 60 minutes. It was not practical for timekeepers to consider minutes until the first mechanical clocks that displayed minutes appeared near the end of the 16th century. By that time, sexagesimal divisions of time were well established in Europe.
   Before time became standardized, clock masters used “True Time”. The day work began and ended with the sun. This time period was divided into 12 equal hours. This meant that these hours would vary with the seasons, as the length of daylight changed. Each town would have their own variance of this “True Time”. Eventually, cities adopted “Mean Time”, which is how we think of time nowadays. Astronomers used the Earth’s rotation and the stars to calculate the time, and divided the day into 24 uniform and equal hours. Geneva was the first city to adopt mean time in 1780, followed by London in 1792, Berlin in 1810, Paris in 1816, and Vienna in 1823.
   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.
   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:
   While the common units of time, minute, hour, day, month and year, are not decimalised, there have been proposals for decimalisation of the time of day and decimal calendar systems. Astronomers use a decimalised Julian day number to record and predict events.
  
  Section::::Decimal currency.
  
  Decimal currencies have sub-units based on a factor of 10. There are most commonly 100 sub-units to the base currency unit, but currencies based on 1,000 sub-units also exist, especially in Arab countries. The Chinese Yuan is widely considered to be the first decimal currency .
  
  For example:
   BULLET::::- French Republican Calendar
  
  BULLET::::- Hexadecimal time
  
  BULLET::::- List of unusual units of measurement
  
  BULLET::::- Metric time
  
  BULLET::::- Stardate
  
  BULLET::::- Unix time
  
  Section::::External links.
  
  BULLET::::- Decimal Now - Website that shows the current decimal time and a converter to and from decimal time
  
  BULLET::::- Modern decimal time watches manufacturer
  
  BULLET::::- Current decimal time, decimal to normal / normal to decimal time converter
  
  Section::::References.
  
  BULLET::::- Notes
  
  BULLET::::- Sources
  
  BULLET::::- National Convention of the French Republic (1793) LE CALENDRIER RÉPUBLICAIN Textes officiels Décrets Relatifs à l'établissement de l'Ère Républicaine published by Philippe Chapelin 2002
   History of timekeeping devices in Egypt
  
  The ancient Egyptians were one of the first cultures to widely divide days into generally agreed-upon equal parts, using early timekeeping devices such as sundials, shadow clocks, and merkhets (plumb-lines used by early astronomers).
  
  Obelisks are used by reading the shadow that it makes. The citizens could divide the day into two parts, and then into smaller hours.
  
  Section::::Sundials and shadow clocks.
   Section::::History.
  
  One of the earliest known uses of the minute (and the second) is found in John of Sacrobosco's "Computus" (ca. 1235), where he used them when discussing the length of the tropical year. No earlier records for the origin of the minute as of the hour and the second of the minute have ever been found. Another motivation that has been suggested for the emergence of these fine divisions of time was the construction of "precision" timepieces (mechanical and water clocks). 
   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. :: GMT is
   Historically, the word "minute" comes from the Latin "pars minuta prima", meaning "first small part". This division of the hour can be further refined with a "second small part" (Latin: "pars minuta secunda"), and this is where the word "second" comes from. For even further refinement, the term "third" ( of a second) remains in some languages, for example Polish ("tercja") and Turkish ("salise"), although most modern usage subdivides seconds by using decimals. The symbol notation of the prime for minutes and double prime for seconds can be seen as indicating the first and second cut of the hour (similar to how the foot is the first cut of the yard or perhaps chain, with inches as the second cut). In 1267, the medieval scientist Roger Bacon, writing in Latin, defined the division of time between full moons as a number of hours, minutes, seconds, thirds, and fourths ("horae", "minuta", "secunda", "tertia", and "quarta") after noon on specified calendar dates.
   Minutes are usually rounded off to the nearest five minutes. In these styles, the word for "minutes" is usually but not always left out. For example (transliterated into English):
  
  BULLET::::- Six (5 am or pm)
  
  BULLET::::- 20 (minutes) past seven
  
  BULLET::::- 10 (minutes) to eight
  
  BULLET::::- A quarter past nine
  
  BULLET::::- A quarter to eleven
  
  BULLET::::- Half two (1:30)
  
  BULLET::::- Five to half three (2:25)
  
  BULLET::::- Five past half four (3:35)
  
  In these styles, the word for "minutes" is usually but not always left out.
  