454:
electromechanical clocks the electricity serves no time keeping function. The timekeeping function is regulated by the pendulum. Near the end of the nineteenth century, the availability of the dry cell battery made it practical to use electric power in clocks. The use of electricity then led to many variations of clock and motor designs. Electromechanical clocks were made as individual timepieces but most commonly were used as integral parts of synchronized time installations. Experience in telegraphy led to connecting remote clocks (slave clocks) via wires to a controlling (master clock) clock. The goal was to create a clock system where each clock displayed exactly the same time. The master and the slaves are electromechanical clocks. The
446:
295:. They use modern low-voltage DC-powered circuitry, which may be supplied by a battery or derived from mains electricity. They are the most common type of clock today. Quartz clocks and watches as supplied by the manufacturer typically keep time with an error of a few seconds per week, although sometimes more. Inexpensive quartz movements are often specified to keep time within 30 seconds per month (1 second per day, 6 minutes per year). Lower error can be achieved by individual calibration if adjustment is possible, subject to the stability of the oscillator, particularly with change in temperature. Higher accuracy is possible at higher cost.
133:
480:
625:
422:, where he developed an electric clock to have the Hipp-Toggle, presented in Berlin at an exhibition in 1843. The Hipp-Toggle is a device attached to a pendulum or balance wheel that electro-mechanically allows occasional impulse or drive to the pendulum or wheel as its amplitude of swing drops below a certain level, and is so efficient that it was subsequently used in electric clocks for over a hundred years. Hipp also invented a small motor and built the chronoscope and the registering
177:
2219:
36:
640:(FERC) to eliminate the TEC. While this would have freed the power companies from the threat of fines and also provided an extremely modest increase in frequency stability, it was also noted that synchronous clocks, which include wall clocks, alarm clocks, and other clocks computing the time on the basis of their electrical power, would accumulate several minutes of error between the semi-annual resets for
340:
2229:
533:
332:
648:(NAESB), a non-governmental organization that is business-oriented, for removing that standard. If the FERC adopts the NAESB petition, TECs will no longer be utilized in the United States and Canada, and clocks timed by them will likely wander uncontrolled until manually reset, however as of 2021 WEQ-006 was still in place. It was noted in a technical paper by employees of the
568:; 60 cycles per second (Hz) in North America and parts of South America, 50 cycles per second in most other countries. The gear train scales this rotation so the minute hand rotates once per hour. Thus the synchronous clock can be regarded as not so much a timekeeper as a mechanical counter, whose hands display a running count of the number of cycles of alternating current.
233:, which was wound up more frequently by an electric motor or electromagnet. This mechanism was more accurate than a mainspring, because the frequent winding averaged out variations in the clock's rate caused by the varying force of the spring as it unwound. It was used in precision pendulum clocks, and in automotive clocks until the 1970s.
390:, a Scottish clock and instrument maker was the first to invent and patent a clock powered by electric current. His original electric clock patent is dated October 10, 1840. On January 11, 1841, Alexander Bain along with John Barwise, a chronometer maker, took out another important patent describing a clock in which an
463:
slave clocks. The slave clocks are connected by wires to the master clock. These systems are found in locations where multiple clocks would be used such as learning institutions, businesses, factories, transportation networks, banks, offices and government facilities. A notable example of this type of system is the
644:. This consequence was reported in the American news media, and the initiative was dropped. However, in late 2016 a similar proposal was again filed by the NERC to the FERC, which was approved two months later. It is contingent upon the removal of the standard WEQ-006, and the NERC also petitioned the
382:
batteries and an oscillating orb. His team produced improved clocks over many years, which were later denoted as "the most elegant and at the same time the most simple movement yet produced by the electric column". Zamboni's clock had a vertical needle supported by a pivot and was so energy efficient
282:
keep time by counting the oscillations of a calibrated tuning fork with a specific frequency. These were only made in battery-powered form. Battery-powered clocks have been made using the schemes above with the obvious exception of a synchronous movement. All battery-powered clocks have been largely
462:
mechanism is not a conventional clock mechanism as it consists only of a ratchet wheel and time train. Slave clocks rely upon electrical impulses from the master clock to mechanically move the clock hands one unit of time. Synchronized time systems are made up of one master clock and any number of
616:
atomic clock time so that the total number of cycles in a day gives an average frequency that is exactly the nominal value, so synchronous clocks do not accumulate error. For example, European utilities control the frequency of their grid once a day to make the total number of cycles in 24 hours
453:
A clock that employs electricity in some form to power a conventional clock mechanism is an electromechanical clock. Any spring or weight driven clock that uses electricity (either AC or DC) to rewind the spring or raise the weight of a mechanical clock then is an electromechanical clock. In
668:
clocks was that the motor could be started in either direction, so if the starter knob was spun the wrong way the clock would run backwards, the hands turning counterclockwise. Later manual-start clocks had ratchets or other linkages which prevented backwards starting. The invention of the
594:
at 60 Hz and 3000 RPM at 50 Hz. However most electric clocks have rotors with more magnetic poles (teeth), consequently rotating at a smaller submultiple of line frequency. This allows the gear train which turns the hands to be built with fewer gears, saving money.
272:. They essentially count cycles of the power supply. While the actual frequency may vary with loading on the grid, the total number of cycles per 24 hours is maintained rigorously constant, so that these clocks can keep time accurately for long periods, barring
611:
of their current to the nominal value of 50 or 60 hertz. Although utility load variations cause frequency fluctuations which may result in errors of a few seconds during the course of a day, utilities periodically adjust the frequency of their current using
517:, providing an energy pulse to the moving oscillator. This oscillator is responsible for the accuracy of the clock. The electronic part would not generate electrical pulses if the oscillator was absent or did not move. The
370:
but the disadvantage of its electrical properties varying with the weather. He trialled various means of regulating the electricity and these models proved to be reliable across a range of meteorological conditions.
909:
884:
436:
invented the first synchronous electric clock in
Ashland, MA, which kept time from the oscillations of the power grid. In 1931, the Synclock was the first commercial synchronous electric clock sold in the UK.
628:
The over 7-minute time error that would have developed in electric clocks over much of N. America had they not been reset after the March 2016 switch to
Daylight Saving Time, and had TEC's not been utilized
673:
allowed self-starting clocks to be made, but since the clock would then restart after a power outage, the clock would give incorrect time instead of being stopped at the time of power interruption.
1194:
656:
that, had TECs not been inserted in 2016, there would have been over seven minutes lost by electrically timed clocks over much of the United States and Canada, as shown in Figure 8 of their paper.
429:
The first electric clocks had prominent pendulums because this was a familiar shape and design. Smaller clocks and watches with a spiral-balance are made on the same principles as pendulum clocks.
471:. These self-winding clock systems were usually low voltage DC. They were installed through the 1950s and by then systems with synchronous motor clocks were becoming the clock system of choice.
645:
571:
One of the gears turning the clock's hands has a shaft with a sliding friction fitting, so the clock's hands can be turned manually by a knob on the back or on the bottom, to set the clock.
969:
251:). This was the mechanism used in the first electric clocks, and is found in antique electric pendulum clocks. It is also found in a few modern decorative mantel and desk clocks.
1127:
404:
Numerous people were intent on inventing the electric clock with electromechanical and electromagnetic designs around the year 1840, such as
Wheatstone, Steinheil, Hipp,
276:; over months they are more accurate than a typical quartz clock. This was the most common type of clock from the 1930s but has now been mostly replaced by quartz clocks.
893:
449:
Master clock from synchronized school clock system. c.1928 Electromechanical movement winds each minute and impulses slave clocks each minute. Operates on 24 Volts DC
664:
The earliest synchronous clocks from the 1930s were not self-starting, and had to be started by spinning a starter knob on the back. A flaw in the design of these
1013:
540:
A synchronous electric clock does not contain a timekeeping oscillator such as a pendulum or balance wheel, but instead counts the oscillations of the AC
160:
were introduced in the 1980s. The first experimental electric clocks were constructed around the 1840s, but they were not widely manufactured until mains
1201:
136:
Telechron synchronous electric clock manufactured around 1940. By 1940, the synchronous clock became the most common type of clock in the United States
633:
985:
is the number of poles on the rotor. Many designs have 30 poles, so that the motor runs at 240 RPM (at 60 Hz) or 200 RPM (at 50 Hz).
649:
739:
17:
1134:
849:
1828:
1664:
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correct. U.S. utilities correct their frequency once the cumulative error has reached 3–10 sec. This correction is known as the
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Some electric clocks have a simple two-pole synchronous motor which runs at one revolution per cycle of power, i.e., 3600
1224:
1293:
1001:
779:
100:
637:
72:
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keep time with a pendulum or balance wheel, but the pulses to keep it going are not provided by a mechanical movement and
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Synchronous motor clocks are rugged because they do not have a delicate pendulum or balance wheel. However, a temporary
1187:
712:
79:
119:
405:
2263:
1021:
1778:
1433:
618:
487:
The configuration of this device is comparatively very simple and reliable. The electric current powers either a
418:, is credited with establishing the production series, mass marketable electric clock. Hipp opened a workshop in
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is employed to keep the clock going instead of springs or weights. Later patents expanded on his original ideas.
53:
86:
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57:
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will stop the clock, which will show the wrong time when power is restored. Some synchronous clocks (e.g.
2031:
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1943:
1823:
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46:
156:. The term is often applied to the electrically powered mechanical clocks that were used before
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1864:
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93:
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1533:
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1279:
641:
367:
196:
8:
1989:
1448:
1408:
359:
265:
262:
857:
132:
1938:
1916:
1783:
1607:
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1506:
1077:
479:
2019:
1898:
1798:
1651:
1554:
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1234:
1229:
775:
737:
Brimarc, typical quartz clock movement specified accurate to within ±30 seconds/month
670:
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311:
269:
258:
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causes the current through the second inductor, and the second inductor works as an
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1953:
1921:
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has a conventional self-winding clock mechanism that is rewound electrically. The
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2041:
2009:
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1911:
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346:
Pulsynetic, C40A, Waiting Train, Turret Clock (1940s/50?). Photographed in the
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244:
216:
161:
829:
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2014:
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1346:
553:
514:
220:
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152:, as opposed to a mechanical clock which is powered by a hanging weight or a
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716:
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are electric clocks which keep time by counting oscillations of a vibrating
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2188:
1854:
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149:
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1999:
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1684:
1468:
549:
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468:
419:
240:
230:
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208:
153:
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in revolutions per minute (RPM) is related to the number of poles by:
229:
have gear trains turned by a small spring or weighted lever, called a
2162:
2079:
1715:
1627:
1602:
1583:
1473:
836:, filed February 26, 1917, issued October 29, 1918, on Google Patents
579:
521:
518:
510:
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273:
188:
Electric clocks can operate by several different types of mechanism:
335:
One of
Alexander Bain's early electromagnetic clocks, from the 1840s
35:
1730:
1573:
1483:
1341:
1331:
1094:
856:. Antiquarian Horological Society, London, UK. 2011. Archived from
488:
394:
379:
378:
of Verona invented and showed another electrostatic clock run with
363:
248:
200:
509:. When the magnet passes the first inductor or sensor, the simple
168:
replaced mechanical clocks as the most widely used type of clock.
2069:
2059:
1981:
1972:
1957:
1844:
1689:
1612:
1321:
582:) have an indicator which shows if it has stopped and restarted.
524:
of the mechanical oscillator should be several times per second.
415:
362:
of London invented the first electric clock. It was powered with
1859:
636:(NERC), a consensus-based industry organization, petitioned the
2167:
1326:
502:
351:
339:
303:
are quartz clocks which are periodically synchronized with the
564:. The rotation rate of the motor shaft is synchronized to the
532:
2177:
1926:
1617:
1565:
331:
164:
became available in the 1890s. In the 1930s, the synchronous
145:
544:
from its wall plug to keep time. It consists of a small AC
1316:
1302:
892:. London: Heywood & Co. pp. 95–100. Archived from
501:
The electromechanical oscillator component has an attached
1109:
613:
1060:
603:
The accuracy of synchronous clocks depends on how close
383:
that it could operate on one battery for over 50 years.
1271:
215:, but use electricity to rewind the mainspring with an
467:, which is an example of an electromechanical gravity
268:
as a timing source, by driving the clock gears with a
938:
772:
Sir
Francis Ronalds: Father of the Electric Telegraph
548:, which turns the clock's hands through a reduction
1078:
http://www.gps.gov/cgsic/meetings/2011/matsakis.pdf
223:. This mechanism is found mostly in antique clocks.
180:Electromechanical self-winding clock movement from
60:. Unsourced material may be challenged and removed.
963:
536:Clock radio with synchronous clock, from the 1950s
1090:"Appliance disruptions feared in power grid test"
2245:
1128:"NAESB Wholesale Electric Quadrant (WEQ) Update"
755:Aked, C.K. (1973). "The First Electric Clock".
634:North American Electric Reliability Corporation
797:"Remembering the First Battery-Operated Clock"
650:National Institute of Standards and Technology
1287:
1209:
1195:
527:
1166:Perpetual Electromotive of Giuseppe Zamboni
1160:Viradez, Michel. History of Electric Clocks
997:
995:
993:
991:
823:
408:, and Garnier, both in Europe and America.
283:replaced by the lower cost quartz movement.
1294:
1280:
1202:
1188:
979:is the line frequency (50/60 Hz) and
440:
960:
318:around the world. They are distinct from
120:Learn how and when to remove this message
988:
623:
531:
478:
474:
444:
338:
330:
175:
131:
1163:Katz, Eugenii. Alexander Bain Biography
1110:"North American Energy Standards Board"
794:
769:
199:, which keeps time with an oscillating
14:
2246:
1225:Synchronous Motor and the Master Clock
1169:Chirkin, K. Electromechanical clocks.
1061:"Federal Energy Regulatory Commission"
878:
876:
874:
1275:
1183:
964:{\displaystyle v={\frac {120f}{p}}\,}
850:"Famous Names in Electrical Horology"
844:
842:
2228:
1014:"Frequency response - National Grid"
882:
754:
704:
659:
646:North American Energy Standard Board
638:Federal Energy Regulatory Commission
58:adding citations to reliable sources
29:
871:
710:
24:
839:
774:. London: Imperial College Press.
585:
483:Early French electromagnetic clock
25:
2275:
924:The speed of a synchronous motor
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2218:
2217:
34:
1120:
1102:
1082:
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1053:
1035:
1006:
918:
903:
715:. Elliott Sound. Archived from
45:needs additional citations for
814:
788:
763:
748:
730:
366:, a high voltage battery with
195:have a traditional mechanical
13:
1:
1154:
257:rely on the 50 or 60 Hz
27:Clock powered by electricity
7:
2032:Geological history of Earth
713:"Build a Synchronous Clock"
676:
598:
10:
2280:
1384:Orders of magnitude (time)
795:Ronalds, B.F. (Jun 2015).
528:Synchronous electric clock
326:
227:Electric remontoire clocks
18:Synchronous electric clock
2213:
2155:
2108:
2095:Time translation symmetry
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1819:
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1340:
1309:
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1211:Electric clock technology
854:Electrical Horology Group
1301:
698:
688:Shortt-Synchronome clock
556:which create a rotating
465:Shortt-Synchronome clock
193:Electromechanical clocks
171:
2264:19th-century inventions
2050:Absolute space and time
1701:Astronomical chronology
886:Electric Clocks, 2nd Ed
820:Perpetual Electromotive
441:Electromechanical clock
300:Radio-controlled clocks
247:from an electromagnet (
2100:Time reversal symmetry
1404:Italian six-hour clock
1218:Powerline synchronized
965:
770:Ronalds, B.F. (2016).
654:U.S. Naval Observatory
629:
552:. The motor contains
537:
484:
450:
426:for time measurement.
355:
336:
237:Electromagnetic clocks
185:
137:
1865:Time and fate deities
1810:The Unreality of Time
1749:A series and B series
1018:www2.nationalgrid.com
966:
899:on February 23, 2014.
627:
619:Time Error Correction
535:
482:
475:Electromagnetic clock
448:
414:, clockmaker born in
342:
334:
179:
135:
2116:Chronological dating
2085:Theory of relativity
1429:Daylight saving time
936:
883:Wise, S. J. (1952).
830:U.S. patent #1283434
801:Antiquarian Horology
757:Antiquarian Horology
642:Daylight Saving Time
560:which turns an iron
54:improve this article
2259:Scottish inventions
1409:Thai six-hour clock
1176:(1968): p. 43.
368:extremely long life
360:Sir Francis Ronalds
350:(The Secretariat),
348:Ministers' Building
344:Gents' of Leicester
266:electric power grid
148:that is powered by
1939:Rosy retrospection
1917:Mental chronometry
1741:Philosophy of time
961:
742:2015-07-04 at the
630:
605:electric utilities
538:
485:
451:
434:Henry Ellis Warren
356:
337:
316:dedicated stations
312:radio time signals
280:Tuning Fork clocks
255:Synchronous clocks
207:powered through a
186:
138:
2241:
2240:
2151:
2150:
2126:Circadian rhythms
1944:Tense–aspect–mood
1799:Temporal finitism
1676:
1675:
1652:Grandfather clock
1269:
1268:
1235:Synchronous motor
1230:Utility frequency
958:
832:Warren, Henry E.
781:978-1-78326-917-4
671:shaded-pole motor
660:Spin-start clocks
566:utility frequency
546:synchronous motor
493:electromechanical
270:synchronous motor
259:utility frequency
130:
129:
122:
104:
16:(Redirected from
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2231:
2230:
2221:
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2138:Glottochronology
1978:
1977:
1894:Human experience
1754:B-theory of time
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1133:. Archived from
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1080:
1075:
1069:
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1057:
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1020:. Archived from
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505:that passes two
399:electric current
376:Giuseppe Zamboni
243:linkage, but by
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69:"Electric clock"
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2200:Time immemorial
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2104:
2065:Coordinate time
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1990:Geological time
1966:
1949:Time management
1912:Generation time
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1098:. 27 June 2011.
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912:Electric Clocks
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744:Wayback Machine
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731:
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693:Automatic watch
679:
662:
601:
588:
586:Number of poles
542:utility current
530:
477:
443:
392:electromagnetic
329:
310:time scale via
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126:
115:
109:
106:
63:
61:
51:
39:
28:
23:
22:
15:
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11:
5:
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2143:Time geography
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2133:Clock reaction
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2110:
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2017:
2012:
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2002:
1997:
1986:
1984:
1975:
1968:
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1965:
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1951:
1946:
1941:
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1932:time signature
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1804:Temporal parts
1801:
1796:
1791:
1786:
1781:
1776:
1774:Eternal return
1771:
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1759:Chronocentrism
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1544:Hindu Panchang
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747:
729:
711:Elliott, Rod.
702:
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661:
658:
600:
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587:
584:
558:magnetic field
554:electromagnets
529:
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476:
473:
442:
439:
388:Alexander Bain
328:
325:
324:
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296:
293:quartz crystal
284:
277:
252:
245:magnetic force
234:
224:
217:electric motor
173:
170:
166:electric clock
162:electric power
142:electric clock
128:
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42:
40:
33:
26:
9:
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3:
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2255:
2254:Clock designs
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2121:Chronobiology
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2055:Arrow of time
2053:
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2048:
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2039:
2033:
2030:
2028:
2027:Geochronology
2025:
2021:
2018:
2016:
2013:
2011:
2008:
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1877:Wheel of time
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1721:Periodization
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1647:Digital clock
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1430:
1427:
1425:
1424:Relative hour
1422:
1420:
1419:24-hour clock
1417:
1415:
1414:12-hour clock
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1162:
1159:
1158:
1140:on 2022-12-06
1136:
1129:
1123:
1115:
1114:www.naesb.org
1111:
1105:
1097:
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1085:
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1056:
1048:
1044:
1038:
1024:on 2017-11-03
1023:
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906:
895:
888:
887:
879:
877:
875:
860:on 2012-05-07
859:
855:
851:
845:
843:
835:
834:Timing device
831:
826:
817:
802:
798:
791:
783:
777:
773:
766:
758:
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741:
738:
733:
719:on 2018-07-11
718:
714:
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703:
694:
691:
689:
686:
684:
681:
680:
674:
672:
667:
657:
655:
651:
647:
643:
639:
635:
632:In 2011, the
626:
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610:
606:
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593:
583:
581:
577:
572:
569:
567:
563:
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551:
547:
543:
534:
525:
523:
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515:electromagnet
512:
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412:Matthäus Hipp
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384:
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353:
349:
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333:
321:
317:
314:broadcast by
313:
309:
306:
302:
301:
297:
294:
290:
289:
288:Quartz clocks
285:
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221:electromagnet
218:
214:
210:
206:
205:balance wheel
202:
198:
194:
191:
190:
189:
183:
178:
169:
167:
163:
159:
158:quartz clocks
155:
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147:
143:
134:
124:
121:
113:
102:
99:
95:
92:
88:
85:
81:
78:
74:
71: –
70:
66:
65:Find sources:
59:
55:
49:
48:
43:This article
41:
37:
32:
31:
19:
2195:Time capsule
2189:Tempus fugit
2187:
2109:Other fields
1808:
1789:Perdurantism
1711:Calendar era
1663:
1656:
1642:Cuckoo clock
1579:astronomical
1553:
1379:Unit of time
1310:Key concepts
1256:Atomic clock
1251:Quartz clock
1210:
1173:
1170:
1142:. Retrieved
1135:the original
1122:
1113:
1104:
1093:
1084:
1073:
1065:www.ferc.gov
1064:
1055:
1047:www.nerc.com
1046:
1037:
1026:. Retrieved
1022:the original
1017:
1008:
981:
980:
975:
974:
926:
925:
920:
911:
910:Wise (1952)
905:
894:the original
885:
862:. Retrieved
858:the original
853:
833:
825:
816:
804:. Retrieved
800:
790:
771:
765:
756:
750:
732:
721:. Retrieved
717:the original
706:
683:Master clock
665:
663:
631:
602:
589:
576:power outage
573:
570:
539:
500:
486:
456:master clock
452:
431:
428:
410:
403:
385:
373:
357:
320:clock radios
308:atomic clock
298:
286:
279:
254:
236:
226:
192:
187:
165:
141:
139:
116:
107:
97:
90:
83:
76:
64:
52:Please help
47:verification
44:
2205:Time travel
2183:System time
2090:Time domain
2075:Proper time
1899:use of time
1870:Father Time
1850:Immortality
1840:Ages of Man
1769:Endurantism
1726:Regnal year
1706:Big History
1635:water-based
1534:Solar Hijri
1444:Hexadecimal
1394:Measurement
1356:Chronometry
1342:Measurement
1261:Radio clock
915:, p.101–104
460:slave clock
424:chronograph
182:Switzerland
150:electricity
2248:Categories
1907:Chronemics
1882:Kalachakra
1794:Presentism
1779:Eternalism
1685:Chronology
1623:mechanical
1574:Main types
1492:Main types
1244:Electronic
1155:References
1144:2022-01-07
1028:2016-06-03
1002:NIST Paper
864:2011-12-16
723:2016-12-13
666:spin-start
550:gear train
496:oscillator
469:remontoire
420:Reutlingen
274:power cuts
241:escapement
231:remontoire
213:mainspring
209:gear train
154:mainspring
110:March 2011
80:newspapers
2163:Leap year
2080:Spacetime
1954:Yesterday
1855:Dreamtime
1829:Mythology
1716:Deep time
1628:stopwatch
1603:hourglass
1584:astrarium
1514:Gregorian
1507:Lunisolar
1484:Calendars
1474:Time zone
1347:standards
609:frequency
607:keep the
580:Telechron
522:frequency
511:amplifier
507:inductors
432:In 1918,
386:In 1840,
374:In 1815,
364:dry piles
358:In 1814,
2223:Category
1971:Time in
1962:Tomorrow
1824:Religion
1764:Duration
1731:Timeline
1665:Timeline
1464:Sidereal
1332:Eternity
1095:CBS News
740:Archived
677:See also
652:and the
599:Accuracy
519:resonant
489:pendulum
395:pendulum
380:dry pile
249:solenoid
201:pendulum
197:movement
2233:Commons
2156:Related
2070:Instant
2060:Chronon
2042:Physics
1982:Geology
1973:science
1845:Destiny
1690:History
1658:History
1613:sundial
1596:quantum
1539:Chinese
1529:Islamic
1439:Decimal
1434:Chinese
1396:systems
1322:Present
621:(TEC).
416:Germany
406:Breguet
397:and an
327:History
261:of the
94:scholar
2173:Moment
2168:Memory
2020:period
1608:marine
1591:atomic
1566:Clocks
1524:Hebrew
1519:Julian
1454:Metric
1327:Future
1171:Radio,
1043:"NERC"
973:where
778:
503:magnet
491:or an
352:Yangon
96:
89:
82:
75:
67:
2178:Space
2010:epoch
2000:chron
1958:Today
1927:tempo
1922:Music
1784:Event
1618:watch
1502:Lunar
1497:Solar
1469:Solar
1459:Roman
1449:Hindu
1138:(PDF)
1131:(PDF)
897:(PDF)
890:(PDF)
806:8 Apr
699:Notes
562:rotor
211:by a
172:Types
146:clock
144:is a
101:JSTOR
87:books
1897:and
1860:Kāla
1555:List
1549:Maya
1345:and
1317:Past
1303:Time
808:2016
776:ISBN
73:news
2015:era
2005:eon
1995:age
1374:TAI
1364:UTC
949:120
614:UTC
592:RPM
305:UTC
219:or
203:or
140:An
56:by
2250::
1960:–
1956:–
1369:UT
1112:.
1092:.
1063:.
1045:.
1016:.
990:^
873:^
852:.
841:^
799:.
498:.
263:AC
1295:e
1288:t
1281:v
1203:e
1196:t
1189:v
1174:7
1147:.
1116:.
1067:.
1049:.
1031:.
982:p
976:f
956:p
952:f
943:=
940:v
927:v
867:.
810:.
784:.
759:.
726:.
354:.
322:.
184:.
123:)
117:(
112:)
108:(
98:·
91:·
84:·
77:·
50:.
20:)
Text is available under the Creative Commons Attribution-ShareAlike License. Additional terms may apply.
