So Man was just kicking along, doing whatever he wanted whenever he wanted and no one around to stress his dawdle with stuff like target-dates or deadlines or fully operational assembly schedules. No no no...wake up when that bright thing in the sky made it hard to sleep, maybe gnaw a fig or some berries then grab your stone-point spear and hunt a mastadon; maybe an auroch or two...A nice braised auroch tail, some tepid water and that's lunch. Tired? No problem, just nap a bit while the womenfolk skin the remaining auroch...Ahhh, soo nice, so very nice.

Until some tank town boob from Scotland - with probably too much time on his hands - just had to go and invent the first clock. That's it just below. And ever since people have been having heart seizures and sprained limbs running for elevators, trains, buses, the last Beanie Baby at the Christmas Shoppe...all because some Mesolithic meddler HAD to know when the Moon was waxing.

It's a brittle thread upon which hangs Humanity; a brittle thread.

British archaeology experts have discovered what they believe to be the world's oldest 'calendar', created by hunter-gatherer societies and dating back to around 8,000 BC.

The Mesolithic monument was originally excavated in Aberdeenshire, Scotland, by the National Trust for Scotland in 2004. Now analysis by a team led by the University of Birmingham, published today (July 15, 2013) in the journal Internet Archaeology, sheds remarkable new light on the luni-solar device, which pre-dates the first formal -measuring devices known to Man, found in the Near East, by nearly 5,000 years.

The mathematician and astronomer Theodosius of Bithynia ( c. 160 BC to c. 100 BC) is said to have invented a universal sundial that could be used anywhere on Earth. The Romans adopted the Greek sundials, and the first record of a sundial in Rome is 293 BCE according to Pliny


World's oldest known sundial, from Egypt's Valley of the Kings (c. 1500 BC), used to measure work hours.[1][2][3

Michael A. Lombardi, a metrologist in the Time and Frequency Division at the National Institute of Standards and Technology in Boulder, Colo., takes the case.

In today's world, the most widely used numeral system is decimal (base 10), a system that probably originated because it made it easy for humans to count using their fingers. The civilizations that first divided the day into smaller parts, however, used different numeral systems, specifically duodecimal (base 12) and sexagesimal (base 60).

Thanks to documented evidence of the Egyptians' use of sundials, most historians credit them with being the first civilization to divide the day into smaller parts. The first sundials were simply stakes placed in the ground that indicated time by the length and direction of the resulting shadow. As early as 1500 B.C., the Egyptians had developed a more advanced sundial. A T-shaped bar placed in the ground, this instrument was calibrated to divide the interval between sunrise and sunset into 12 parts. This division reflected Egypt's use of the duodecimal system--the importance of the number 12 is typically

attributed either to the fact that it equals the number of lunar cycles in a year or the number of finger joints on each hand (three in each of the four fingers, excluding the thumb), making it possible to count to 12 with the thumb. The next-generation sundial likely formed the first representation of what we now call the hour. Although the hours within a given day were approximately equal, their lengths varied during the year, with summer hours being much longer than winter hours.

Without artificial light, humans of this time period regarded sunlit and dark periods as two opposing realms rather than as part of the same day. Without the aid of sundials, dividing the dark interval between sunset and sunrise was more complex than dividing the sunlit period. During the era when sundials were first used, however, Egyptian astronomers also first observed a set of 36 stars that divided the circle of the heavens into equal parts. The passage of night could be marked by the appearance of 18 of these stars, three of which were assigned to each of the two twilight periods when the stars were difficult to view. The period of total darkness was marked by the remaining 12 stars, again resulting in 12 divisions of night (another nod to the duodecimal system). During the New Kingdom (1550 to 1070 B.C.), this measuring system was simplified to use a set of 24 stars, 12 of which marked the passage of the night. 

Once both the light and dark hours were divided into 12 parts, the concept of a 24-hour day was in place. The concept of fixed-length hours, however, did not originate until the Hellenistic period, when Greek astronomers began using such a system for their theoretical calculations. Hipparchus, whose work primarily took place between 147 and 127 B.C., proposed dividing the day into 24 equinoctial hours, based on the 12 hours of daylight and 12 hours of darkness observed on equinox days. Despite this suggestion, laypeople continued to use seasonally varying hours for many centuries. (Hours of fixed length became commonplace only after mechanical clocks first appeared in Europe during the 14th century.)

Hipparchus and other Greek astronomers employed astronomical techniques that were previously developed by the Babylonians, who resided in Mesopotamia. The Babylonians made astronomical calculations in the sexagesimal (base 60) system they inherited from the Sumerians, who developed it around 2000 B.C. Although it is unknown why 60 was chosen, it is notably convenient for expressing fractions, since 60 is the smallest number divisible by the first six counting numbers as well as by 10, 12, 15, 20 and 30.

Although it is no longer used for general computation, the sexagesimal system is still used to measure angles, geographic coordinates and time. In fact, both the circular face of a clock and the sphere of a globe owe their divisions to a 4,000-year-old numeric system of the Babylonians.

The Greek astronomer Eratosthenes (who lived circa 276 to 194 B.C.) used a sexagesimal system to divide a circle into 60 parts in order to devise an early geographic system of latitude, with the horizontal lines running through well-known places on the earth at the time. A century later, Hipparchus normalized the lines of latitude, making them parallel and obedient to the earth's geometry. He also devised a system of longitude lines that encompassed 360 degrees and that ran north to south, from pole to pole. In his treatise Almagest (circa A.D. 150), Claudius Ptolemy explained and expanded on Hipparchus' work by subdividing each of the 360 degrees of latitude and longitude into smaller segments. Each degree was divided into 60 parts, each of which was again subdivided into 60 smaller parts. The first division, partes minutae primae, or first minute, became known simply as the "minute." The second segmentation, partes minutae secundae, or "second minute," became known as the second Minutes and seconds, however, were not used for everyday timekeeping until many centuries after theAlmagest.Clock displays 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 the general public to consider minutes until the first mechanical clocks that displayed minutes appeared near the end of the 16th century. Even today, many clocks and wristwatches have a resolution of only one minute and do not display seconds.

Thanks to the ancient civilizations that defined and preserved the divisions of time, modern society still conceives of a day of 24 hours, an hour of 60 minutes and a minute of 60 seconds. Advances in the science of timekeeping, however, have changed how these units are defined. Seconds were once derived by dividing astronomical events into smaller parts, with the International System of Units (SI) at one time defining the second as a fraction of the mean solar day and later relating it to the tropical year. This changed in 1967, when the second was redefined as the duration of 9,192,631,770 energy transitions of the cesium atom. This recharacterization ushered in the era of atomic timekeeping and Coordinated Universal Time (UTC).

Interestingly, in order to keep atomic time in agreement with astronomical time, leap seconds occasionally must be added to UTC. Thus, not all minutes contain 60 seconds. A few rare minutes, occurring at a rate of about eight per decade, actually contain 61.

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  • Time's Pendulum. Jo Ellen Barnett. Plenum Press, 1998.
  • A History of Mathematics. Florian Cajori. MacMillan and Co., 1894.
  • History of the Hour. Gerhard Dohrn-van Rossum. University of Chicago Press, 1996.


Check current time anywhere, convert between time zones. Click link above.

  • Because the second is based on the number of times the cesium atom transitions between the two hyperfine levels of its ground state compared to ephemeris time, and the fact that the earth’s rotation is slowing down, it becomes necessary to add periodic “leap seconds” into the atomic timescale to keep the two within one second of each other.
  • Since 1972 to 2006 there have been 23 leap seconds added, ranging from one every 6 months to 1 every 7 years.
  • The International Earth Rotation and Reference Systems Service (IERS) is the organization which monitors the difference in the two timescales and calls for leap seconds to be inserted or removed when necessary.
  • Although it is not a standard defined by the International System of Units, the hour is a unit accepted for use with SI, represented by the symbol h.
  • In astronomy, the Julian year is a unit of time, defined as 365.25 days of 86400 SI seconds each.
  • It is though that the moon was used to calculate time as early as 10,000-28,000 BC. Lunar calendars were among the first to appear, either 12 or 13 lunar months (either 346 or 364 days). Lunisolar calendars often have a thirteenth month added to some years to make up for the difference between a full year (now known to be about 365.24 days) and a year of just twelve lunar months. The numbers twelve and thirteen came to feature prominently in many cultures, at least partly due to this relationship of months to years.

TheAntikythera mechanism(/ˌæntɪkɪˈθɪərə/AN-tə-kə-THEER-ə) is an ancient Greek hand-poweredorrery, described as the firstanalogue computer,[1]the oldest known example of such a device[2][3][4][5][6][7][8][9]used to predictastronomicalpositions andeclipsesforcalendarandastrologicalpurposes decades in advance.[10][11][12]It could also be used to track the four-year cycle of athletic games which was similar to anOlympiad, the cycle of theancient Olympic Games.[13][1

This modern reconstruction shows  a complex clockwork mechanism composed of at least 30 meshing bronze gears. In 2008, a team led by Mike Edmunds and Tony Freeth at Cardiff University used modern computer x-ray tomography and high resolution surface scanning to image inside fragments of the crust-encased Mechanism and read the faintest inscriptions that once covered the outer casing of the machine.

Detailed imaging of the mechanism suggests that it had 37 gear wheels enabling it to follow the movements of the Moon and the Sun through the zodiac, to predict eclipses and even to model the irregular orbit of the Moon, where the Moon's velocity is higher in its perigee than in its apogee. This motion was studied in the 2nd century BC by astronomer Hipparchus of Rhodes, and it is speculated that he may have been consulted in the machine's construction.

Generally speaking, methods of temporal measurement, or chronometry, take two distinct forms: the Calendar, a mathematical tool for organising intervals of time,[19] and the Clock, a physical mechanism that counts the passage of time. In day-to-day life, the Clock is consulted for periods less than a day whereas the Calendar is consulted for periods longer than a day. Increasingly, personal electronic devices display both Calendars and Clocks simultaneously. The number (as on a clock dial or calendar) that marks the occurrence of a specified event as to hour or date is obtained by counting from a fiducial epoch – a central reference point.