As of the 2010s, atomic clocks are the most accurate clocks in existence. They are considerably more accurate than quartz clocks as they can be accurate to within a few seconds over thousands of years.[54] Atomic clocks were first theorized by Lord Kelvin in 1879.[55] In the 1930s the development of Magnetic resonance created practical method for doing this.[56] A prototype ammonia maser device was built in 1949 at the U.S. National Bureau of Standards (NBS, now NIST). Although it was less accurate than existing quartz clocks, it served to demonstrate the concept.[57][58][59] The first accurate atomic clock, a caesium standard based on a certain transition of the caesium-133 atom, was built by Louis Essen in 1955 at the National Physical Laboratory in the UK.[60] Calibration of the caesium standard atomic clock was carried out by the use of the astronomical time scale ephemeris time (ET).[61] As of 2013, the most stable atomic clocks are ytterbium clocks, which are stable to within less than two parts in 1 quintillion (2×10−18).[62]


Synchronous electric clocks do not have an internal oscillator, but count cycles of the 50 or 60 Hz oscillation of the AC power line, which is synchronized by the utility to a precision oscillator. The counting may be done electronically, usually in clocks with digital displays, or, in analog clocks, the AC may drive a synchronous motor which rotates an exact fraction of a revolution for every cycle of the line voltage, and drives the gear train. Although changes in the grid line frequency due to load variations may cause the clock to temporarily gain or lose several seconds during the course of a day, the total number of cycles per 24 hours is maintained extremely accurately by the utility company, so that the clock keeps time accurately over long periods.
You’re going to have to admit it to yourself at one point or another—using your smartphone as a digital alarm clock just doesn’t cut it. You sleep through it, you rely on it as a bedroom clock when it’s just not cutting it. Whether you need alarm clocks for heavy sleepers, a projection alarm clock, or a programmable alarm clock that is up to you. You just need to make sure that it works. Fortunately, you know your favorite Gear Hungry experts have whipped up the ten best alarm clock models on the internet.
You can set the clock to release aromatherapeutic scents in tandem with the light, choosing from four different fragrances that come with the clock or using your own essential oil blend. Fifteen minutes before your wake-up time, it'll also emit your choice of soft nature noises. The cycle ends with a chiming noise that gradually grows in volume to ensure that even the heaviest sleepers will wake up.

For light sleepers, audio alarms can be rather jarring. Fortunately, the Philips Morning Wake-Up Light uses a warm, gentle glow and natural sound effects rather than incessant beeping to get you out of bed. The alarm clock also features a colored sunrise simulation and 20 brightness settings for optimal customization. The light slowly increases in brightness between 20 and 40 minutes prior to your desired alarm time. The clock helps you drift to sleep, too. Instead of you simply turning out the lights and settling into bed, the light-responsive dimming feature gently guides you to sleep with audio accompaniment. This type of alarm is definitely not for everyone, but it is suitable for those who prefer to wake up gradually. For more details, read our full Philips Wake-Up Light review.
If you’re looking for a way to add some pizazz to your walls as well as some function, wall clocks are a great design choice. You can find a wall clock in almost every shape, style and color. From modern wall clocks like the sunburst clock to antique wall clocks such as the pendulum clock, there’s a style for every room and every home. Some are even designed to fit into specific rooms: there are dozens of kitchen clocks featuring faces shaped like teapots, cows, bottles of milk and more. There’s even incentive to go big, as large wall clocks can become a statement piece in the same way a large mirror or work of art can.
Stay punctual with an alarm clock! They are great for waking you up in the morning or simply reminding you of special events. These items are a household must-have! Perfect for bedside nightstands, most alarm clocks feature a built-in FM radio to enjoy your favorite radio station, as well as a snooze button for when you need 5 to 10 minutes more sleep. iHome? clock radios have dock for MP3 players to listen to music through the speakers. Choose from a variety of unique, creative designs that are great for virtually any d‚cor.
The naysayers might note that your cell phone alarm can already be set to vibrate, so why not just slip your smartphone under your pillowcase? All sanitary arguments aside, the SmartShaker 2 vibrates much more powerfully than a standard smartphone (three times more to be exact). The SmartShaker 2 also connects to your smartphone via Bluetooth and incorporates a functional, easy-to-use app that’s available for both Android and iOS devices. You can even set up to 10 different alarms and choose from an array of options, just in case you want an audio alarm as well as a vibration. After all, sometimes the snooze struggle is all too real.

Never squint to see what time it is again, especially when you're waking up 20 times in the middle of the night to, you know, see exactly what time it is. We love the projection feature that displays the time on your wall or ceiling for easy viewing. Plus, it'll even toss up the temperature — so you'll already know what you should wear to work before you even get out of bed.
This isn’t for just any old sleeper. This is going to ensure that you get up with every bit of vigor in its little electronic body. Sonic Alert brings us a seriously powerful alarm clock that actually shakes the bed to get you out of it, and comes with a large red LCD screen. You’ll have red flashing in your eyes, the bed rumbling, and a loud sound as the light pulsates to get you up. The world isn’t ending, you’re just getting up for work again. Look alive, tiger!
Some water clock designs were developed independently and some knowledge was transferred through the spread of trade. Pre-modern societies do not have the same precise timekeeping requirements that exist in modern industrial societies, where every hour of work or rest is monitored, and work may start or finish at any time regardless of external conditions. Instead, water clocks in ancient societies were used mainly for astrological reasons. These early water clocks were calibrated with a sundial. While never reaching the level of accuracy of a modern timepiece, the water clock was the most accurate and commonly used timekeeping device for millennia, until it was replaced by the more accurate pendulum clock in 17th-century Europe.
The naysayers might note that your cell phone alarm can already be set to vibrate, so why not just slip your smartphone under your pillowcase? All sanitary arguments aside, the SmartShaker 2 vibrates much more powerfully than a standard smartphone (three times more to be exact). The SmartShaker 2 also connects to your smartphone via Bluetooth and incorporates a functional, easy-to-use app that’s available for both Android and iOS devices. You can even set up to 10 different alarms and choose from an array of options, just in case you want an audio alarm as well as a vibration. After all, sometimes the snooze struggle is all too real.
If you've moved away from using a clock completely and instead set an alarm on your phone, consider the SmartShaker by iLuv. The device slides under your pillow and shakes you awake when your phone alarm goes off (it connects wirelessly using bluetooth). You can also have the device sound an audible alarm. The battery lasts a full month before needing to be charged.
Bolter, David J. Turing's Man: Western Culture in the Computer Age. The University of North Carolina Press, Chapel Hill, N.C. (1984). ISBN 0-8078-4108-0 pbk. Very good, readable summary of the role of "the clock" in its setting the direction of philosophic movement for the "Western World". Cf. picture on p. 25 showing the verge and foliot. Bolton derived the picture from Macey, p. 20.
Hang clocks in places where they’ll be most useful, such as the kitchen or above your desk. They should be easily visible and complement the design of the space. Large wall clocks are ideal for over a fireplace, above an entry table or showcased in an art niche. Smaller wall clocks can be added to your kitchen, home office or child’s bedroom to help keep your day on track.
For convenience, distance, telephony or blindness, auditory clocks present the time as sounds. The sound is either spoken natural language, (e.g. "The time is twelve thirty-five"), or as auditory codes (e.g. number of sequential bell rings on the hour represents the number of the hour like the bell, Big Ben). Most telecommunication companies also provide a speaking clock service as well.
A water-powered cogwheel clock was created in China in AD 725 by Yi Xing and Liang Lingzan. This is not considered an escapement mechanism clock as it was unidirectional, the Song dynasty polymath and genius Su Song (1020–1101) incorporated it into his monumental innovation of the astronomical clock-tower of Kaifeng in 1088.[19][page needed] His astronomical clock and rotating armillary sphere still relied on the use of either flowing water during the spring, summer, autumn seasons and liquid mercury during the freezing temperature of winter (i.e. hydraulics). A mercury clock, described in the Libros del saber, a Spanish work from 1277 consisting of translations and paraphrases of Arabic works, is sometimes quoted as evidence for Muslim knowledge of a mechanical clock. A mercury-powered cogwheel clock was created by Ibn Khalaf al-Muradi[20][21]
About 1581 Galileo noticed the characteristic timekeeping property of the pendulum. The Dutch astronomer and physicist Christiaan Huygens was responsible for the practical application of the pendulum as a time controller in clocks from 1656 onward. Huygens’s invention brought about a great increase in the importance and extent of clock making. Clocks, weight-driven and with short pendulums, were encased in wood and made to hang on the wall, but these new eight-day wall clocks had very heavy weights, and many fell off weak plaster walls and were destroyed. The next step was to extend the case to the floor, and the grandfather clock was born. In 1670 the long, or seconds, pendulum was introduced by English clock makers with the anchor escapement.
In China, a striking clock was devised by the Buddhist monk and inventor Yi Xing (683–727).[5] The Chinese engineers Zhang Sixun and Su Song integrated striking clock mechanisms in astronomical clocks in the 10th and 11th centuries, respectively.[6] A striking clock outside of China was the water-powered clock tower near the Umayyad Mosque in Damascus, Syria, which struck once every hour. It was constructed by the Arab engineer al-Kaysarani in 1154. In 1235, an early monumental water-powered alarm clock that "announced the appointed hours of prayer and the time both by day and by night" was completed in the entrance hall of the Mustansiriya Madrasah in Baghdad.[7]
If you’re looking for a calmer start to your day, you might want to try the Wake-Up Light. It gradually gets you up and out of bed with a colored sunrise simulation and a selection of nature-inspired sounds, so that you can start the day feeling refreshed and energized—as if you had woken up naturally. For anyone who finds it particularly hard to get out of bed when it’s cold and dark out, this alarm clock makes those winter mornings that little bit easier. It also comes with a nighttime dimming feature so that you can make sure you’re getting your best night’s rest.
Keep track of time and exude antiqued style with this bold 24-inch oversized wall clock. Crafted from metal and wood, this round analog clock operates on quartz crystal movement and is embellished with a white background and black needles. Roman numerals lend a traditional touch, and small geometric details add extra dimension to the piece. Use this piece to help create a chic French countryside aesthetic in your kitchen. Start by painting the walls a light gray or beige tone with white trim....

The late Roman statesman Cassiodorus (c. 485–585) advocated in his rulebook for monastic life the water clock as a useful alarm for the 'soldiers of Christ' (Cassiod. Inst. 30.4 f.).[4] The Christian rhetorician Procopius described in detail prior to 529 a complex public striking clock in his home town Gaza which featured an hourly gong and figures moving mechanically day and night.[4]
Stay on schedule and charge a range of devices with this innovative iHome dual-alarm clock. Place your compatible smartphone on top of the Qi-certified device for swift wireless charging, or plug your phone into the clock’s handy powered USB port. This iHome dual-alarm clock incorporates NFC technology, so you can connect an array of Bluetooth-enabled devices with a quick touch.
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