Clock Calendar Temp
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 New Desktop Changing Color LED Light Alarm Clock Pen Holder Calendar Temperature  US $6.99
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 La Crosse Technology Atomic Digital Wall Clock US $24.55
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 Glowing LED Change 7 Color Digital Alarm Clock and Temp US $4.39
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 NEW SkyScan Atomic Digital Clock Indoor Outdoor Temp Sensor US $35.95
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 La Crosse Technology Atomic Digital Wall Clock with Temp and Weather Forecast US $37.50
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 JUMBO DISPLAY RADIO CONTROLLED ATOMIC ALARM CLOCK with CalendarTemp Humidity US $25.00
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 Digital Clock Calendar Temp Alarm Count Down Or Up Timer Wall Or Stand Indoor US $18.95
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 LCD Thermometer Hygrometer hign low Temp Humidity Clock shipped same day USA US $9.85
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 Dual Projector LCD ALARM CLOCK calendar thermometer US $8.79
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 LCD DIGITAL BACKLIGHT ALARM CLOCK W DATE TEMP HM006 2 US $7.49
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 La Crosse Technology Atomic Digital Wall Clock with Moon Phase Temp US $32.99
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 NEW White SkyScan Atomic Digital Clock Indoor Outdoor Temp Sensor US $35.95
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 La Crosse Technology Atomic Digital Wall Clock with Date and Temp Display US $24.99
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 NEW Black SkyScan Atomic Digital Clock Wireless Indoor Outdoor Temp US $35.50
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 alarm clock w calendartemp message station 3 magnetic hanging key chainsUSA US $16.49
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 New Mini Grow LED Four Sided Alarm Temperature Calendar Timer Clock White US $2.25
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 La Crosse Technology WT 8005U S Atomic Digital Wall Clock w Temp Silver US $27.74
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 New 7 LED Color Change Digital Alarm Thermometer Clock Temp US $3.98
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 DIGITAL ATOMIC WALL CLOCK with IN OUTDOOR TEMP FORECAST US $49.95
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 Multifunction Home Office Desk Clock Tower Calendar Alarm Temp Timer More US $9.99
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 1pc multifunctional Four sided Alarm Calendar Timer Temperature Clock Brand New US $4.59
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 Hot Pink multifunctional Four sided Alarm Calendar Timer Temperature Clock New US $4.59
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 LaCrosse Atomic Digital Wall Clock w Indoor Temperature US $32.79
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 Digital Thermometer Clock Calendar with Floater US $19.95
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 W 8685 Wireless Indoor Outdoor Thermometer Clock W8685 US $18.10
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 Wireless Silver Sun Moon Forecast Station Atomic Clock with Oscar Outlook US $37.99
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 La Crosse Technologies 27904 ELC 12 Metal Outdoor Clock US $34.26
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 LCD Digital Desktop Alarm Clock Thermometer Hygrometer US $13.99
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 Chaney Instruments Acu Rite Wireless Weather Forecaster With Remote Sensor US $64.99
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 NIB COMBO CLOCK ALARM TEMP DISPLAY NIGHTLIGHT NICE US $3.99
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 La Crosse Technology Atomic Digital Wall Clock with Indoor Temperature Silver US $34.99
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 La Crosse Technology Atomic Digital Wall Clock with Indoor Temperature Black US $34.99
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 Oregon Scientific RMR683HGA Wireless In Outdoor Thermom US $50.96
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 La Crosse Technologies 27906 ELC 18 US $43.15
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 SILVER ATOMIC DIGITAL WALL CLOCK W INDOOR TEMPERATURE US $38.99
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 GENEVA 12 Black Plastic Wall Clock BatteryOp Temp Humidity GlassLens MetalHands US $24.99
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 La Crosse Technology Atomic Digital Wall Clock BLACK US $27.99
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 Touch Control 7 Color Change LED Digital Alarm Clock Calendar Timer Temp US $12.99
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 Glowing LED 7 Color Change Digital Time Data Week Temperature Alarm Clock US $5.12
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 Brand New Lacrosse Technology WT 8005U 9 Inch Digital Atomic Wall Clock Black US $29.63
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 Brand New Lacrosse Technology WT 8005U 9 Inch Digital Atomic Wall Clock Silver US $29.63
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 Lacrosse Technology WT 8005U B 9 Inch Digital Atomic Wall Clock Black US $36.22
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 Meade Instruments Corporation Slim Line Station with IN OUT Temp Humid US $44.84
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 Lacrosse Technology WT 8005U 9 Inch Digital Atomic Wall Clock US $28.41
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 La Crosse Technology Black Model WT 8005 Atomic Digital Wall Clock w Temp US $19.99
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 La Crosse WT 8005U B Digital Atomic Wall Clock US $24.99
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 TimeTemperature Dual Projector LCD ALARM CLOCK calendar thermometer snooze US $17.31
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 Brand New Bell Howell LCD Multi Fuction Alarm Clock With Temp Humidity Calendar US $10.00
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 New Home Temperature Humidify Hygro Meter C F US $4.49
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 La Crosse Technology Atomic Digital Wall Clock w Indoor Temperature Silver US $29.63
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 Kitchen Craft Digital Talking Recordable Kitchen Timer Clock Alarm Temp NEW US $11.99
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 New Multifunction Digital LED Desk Clock Alarm Timer Thermometer Calendar Temp US $11.40
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 Functional Digital LED Alarm Clock Timer Thermometer Calendar Temp US $7.80
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 Lacrosse Technology WT 8005U S 9 inch Digital Atomic Wall Clock Silver US $31.15
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 La Crosse Technology WS 8119U IT CHO Atomic Clock w Temp Brown B004QM97GQ US $52.78
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 Digital Display Atomic Wall Clock 9 Inch Mount or Stand Date Alarm Temperature US $37.99
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 Mounted Home Indoor Temperature Alarm Clock Universal Time Date Automatic NEW US $37.42
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 La Crosse Technology Atomic Digital Wall Clock Model WS 8157OAK IT US $37.95
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 La Crosse Technology WS 8119U IT W Atomic Digital Wall Clock w Temp White US $68.80
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 La Crosse Technology WS 8119U IT B Atomic Digital Wall Clock w Temp Black US $53.81
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 Meade Instruments Corporation MEA TE346W Slim Line Station with Time Temp Foreca US $55.12
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 Meade Instruments Corporation MEA TE256W Slim Line Station with IN OUT Temp Humi US $53.81
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 Digital Alarm Clock and Temp Glowing LED Change 7 Color US $4.99
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 LED variety 7Color Digital Alarm Clock and Temp Glowing US $4.99
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 NEW Forecast Station WS 9611TWC IT TBP US $42.48
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 New Mini Grow LED Four Sided Alarm Temperature Calendar Timer Clock Hot Pink US $2.25
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 NEW LaCrosse Technology Atomic Digital Wall Clock US $35.99
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 La Crosse Atomic Wall Clock Watch Indoor Outdoor Temp US $55.99
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 Skyscan Atomic Clock With Outside Temp US $38.00
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 NEW White SkyScan Atomic Digital Clock Wireless Indoor Outdoor Temp US $35.50
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 Glowing Color Changing LED Cube Digital Alarm Clock New US $.99
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 La Crosse Technologies 65904 ELC Solar Executive Clock Temp Kit US $34.68
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 3 Digital Desk Multi function Temp Timer Time Clocks US $5.95
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 La Crosse Technology WT 8005U S Atomic Digital Wall Clo US $32.39
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 Ladder Travel Alarm Clock Thermometer Fahrenheit Temp US $9.99
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 LCD DIGITAL BACKLIGHT ALARM CLOCK W DATE TEMP HM006 3 US $7.49
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 La Crosse Wall Atomic Clock Alarm Radio Temperature US $33.72
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History of Horology; Sundials to Atomic Clocks
Mankind has always been preoccupied with measuring and recording the passage of time. Timekeeping has been essential for the development of civilisations; from knowing when to plant or harvest crops to identifying important events in the year.
Time has historically been measured in relation to the movement of the Earth; a day, is one revolution of the planet; while a year is an entire orbit of the Sun. Calendars were developed from as far back as 20,000 years ago when hunter-gatherers scratched lines and gouged holes in sticks and bones to possibly count the days between phases of the moon.
Civilizations from the Ancient Egyptians to the Roman Empire have used differing methods to discover what day of the year it is. However, measuring time as it passed throughout the day had always proved difficult to early mankind. Sundials were perhaps the first time pieces and they can trace their origin back over five thousand years; when obelisks were built, possibly to allow the telling of time by the cast of their shadows.
However, the time told on a sundial was based on the movement of the sun in the sky, which would differ throughout the seasons and of course would not work on cloudy days or at night. Other methods such as water clocks or the hourglass would simply act as crude timers. Telling the time of day would prove difficult with people relying on comparisons as time references such as: “As long as it would take a man to walk a quarter mile.”
People were reliant on these methods and others such as bell ringing to indicate important moments until the 14th century, when mechanical clocks first appeared which were driven by weight and regulated by a verge-and-foliot escapement (a gear system that advancing the gear train at regular intervals or 'ticks'). These clocks were far more reliable than sundials or other methods allowing accurate and reliable telling of the time of day for the first time in human history.
The next step forward in horology came in the 17th century when the pendulum was developed to help clocks maintain their accuracy. Clock making soon became widespread and it was not for another three hundred years that the next revolutionary step in horology would take place; with the development of electronic clocks. These were based on the movement of a vibrating crystal (usually quartz) to create an electric signal with an exact frequency.
While electronic clocks were far more accurate than mechanical clocks it wasn’t until the development of Atomic Clocks and around fifty years ago that modern technologies such as communication satellites, GPS and global computer networks became possible.
Most atomic clocks use the resonance of the atom caesium-133 which vibrates exactly at a frequency of 9,192,631,770 every second. Since 1967 the International System of Units (SI) has defined the second as that number of cycles from this atom which makes atomic clocks (sometimes called caesium oscillators) the standard for time measurements.
Atomic clocks are accurate to less than 2 nanoseconds per day, which equates to about one second in 1.4 million years. Because of this accuracy, a universal time scale UTC (Coordinated Universal Time or Temps Universel Coordonné) has been developed that maintains a continuous and stable time scale and supports such features as leap seconds - added to compensate for the slowing of the Earth’s rotation.
However, atomic clocks are extremely expensive and are generally only to be found in large-scale physics laboratories. However, NTP servers (Network Time Protocol), the standard means for achieving time synchronisation on computer networks, can synchronise networks to an atomic clock by using either the Global Positioning System (GPS) network or specialist radio transmissions.
The development of atomic clocks, GPS and NTP time servers has been vital for modern technologies, allowing computer networks all over the world to be synchronized to UTC.
About the Author
Copyright 2008 © Richard N Williams
Richard N Williams is a technical author and a specialist in the telecommunications and network time synchronisation industry helping to develop dedicated time server products; ethernet clocks, GPS time servers, NTP servers, digital wall clocks, atomic clock servers and SNTP time servers. Please visit us for more information about NTP products and NTP servers This article may be republished and reprinted in its complete form or in part without seeking permission providing a relevant link to this site is maintained. It is a violation of copyright law to reprint or publish this content without following these terms.
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