An alarm clock (alarm for short) is a clock that is designed to alert an individual or group of individuals at specified time. The primary function of these clocks is to awaken people from their night's sleep or short naps; they are sometimes used for other reminders as well. Most use sound; some use light or vibration. Some have sensors to identify when a person is in a light stage of sleep, in order to avoid waking someone who is deeply asleep, which causes tiredness, even if the person has had adequate sleep. To stop the sound or light, a button or handle on the clock is pressed; most clocks automatically stop the alarm if left unattended long enough. A classic analog alarm clock has an extra hand or inset dial that is used to specify the time at which to activate the alarm. Alarm clocks are also found on mobile phones, watches, and computers.

Coordinated Universal Time offset UT ΔT DUT1 International Earth Rotation and Reference Systems Service ISO 31-1 ISO 8601 International Atomic Time 6-hour clock 12-hour clock 24-hour clock Barycentric Coordinate Time Barycentric Dynamical Time Civil time Daylight saving time Geocentric Coordinate Time International Date Line Leap second Solar time Terrestrial Time Time zone 180th meridian


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Some clocks, usually digital ones, include an optical projector that shines a magnified image of the time display onto a screen or onto a surface such as an indoor ceiling or wall. The digits are large enough to be easily read, without using glasses, by persons with moderately imperfect vision, so the clocks are convenient for use in their bedrooms. Usually, the timekeeping circuitry has a battery as a backup source for an uninterrupted power supply to keep the clock on time, while the projection light only works when the unit is connected to an A.C. supply. Completely battery-powered portable versions resembling flashlights are also available.

The origin of the all-mechanical escapement clock is unknown; the first such devices may have been invented and used in monasteries to toll a bell that called the monks to prayers. The first mechanical clocks to which clear references exist were large, weight-driven machines fitted into towers and known today as turret clocks. These early devices struck only the hours and did not have hands or a dial.

An on-trend take on a retro design, this 12" round wall clock brings a splash of color to any space in your home. This budget-friendly accent showcases a circular face bordered by alternating blocks of green, blue, and red hues with black Roman numerals in the center. Its plastic frame ensures that it’s lightweight and easy to hang, while its metallic pierced hands offer subtle shimmer. This piece does not include batteries.

"Very easy to use...Excellent Product...I cannot say enough about this clock -I love the fact mum is hearing my voice on a daily basis even though I live in another country....it's truly a great concept - great design and well worth it for elderly - for dementia patients or even for individuals who need a talking reminder about daily tasks or appts."
More than just a time teller, oversized wall clocks create an eye-catching centerpiece in any ensemble while helping define your space’s aesthetic. Take this one for example: made from iron, it’s the perfect pick for any modern farmhouse-inspired decor. It strikes a circular silhouette and has an open and airy feel. Roman numeral accents line the periphery while two spade hands keep tabs on the time. It measures 30'' W x 30'' H x 1'' D and is operated by AA batteries.
The Mood Light Dual Radio with Nature Sounds Tabletop Clock will literally brighten your day with its color changing led and an easy-to-read 0.7” blue led display, and easy access top mounted touch controls. This model has a lot of unique features that set it apart from other clock radios, such as soothing nature sounds (brook/bubbles/forest), a multi-color led mood lamp and built-in 1 AMP charging port for charging your phone while you sleep. You can listen to your favorite FM or connect...
It’s vital to your personal health. When you rest at night, after about twenty to thirty minutes, your body begins to enter REM sleep (if you’re lucky). Either way, your body slows down. Your heart rate hits around 40-50 BPM when you’re sleeping, compared to the 60-100 BPM you go through while you’re awake. This gives your body time to give your heart a rest, repair blood vessels, and repair muscle tissue if you worked out, or physically strained yourself during the day.
Mixing modern minimalism with industrial influence, this round 28" wall clock is as much a decorative accent as it is a practical timepiece. Crafted from metal, it showcases sizable Roman numerals and small spade-style hands to help you keep an eye on the hour. Its black and gold finish gives it an antiqued appearance, while its open design ensures it won’t overwhelm your arrangement. This piece requires two AA batteries (not included) to operate.
In order to shut off this loud alarm, you have to actually get out of bed and stand on the rug for three seconds. But if you find yourself cheating your alarm by crawling back into bed after those few seconds, you can extend the alarm for up to 30 seconds, ensuring you’ll be much more awake once the blood starts flowing to the other parts of your body.
This Technology Curved Tabletop Clock and weather instrument offers curve-appeal. It also offers dynamic white LED display with a mirrored lens which can be seen from across the room and in darkened rooms. Features dual alarms with adjustable settings: HI/LO sound volume, programmable alarm days, snooze duration (5-60 mins), and auto-dim. Displays your current indoor temperature (F only) and humidity and can charge a mobile device with a bonus USB port in the back of the clock. Table standing...

Who doesn't love an alarm clock that verbally lets you know it's time to get up and start your day? Step aside, Siri, because "Reminder Rosie" is where it's at. You can easily record up to 25 different alarm-reminders at 6 seconds each. So why not wake up to a recording of your kids saying, "Good morning, Mom!"? (Or maybe you don't want that.) We love how you can turn off the alarm by quickly pressing a button or just saying out loud, "Reminder Off." 


Some clocks, usually digital ones, include an optical projector that shines a magnified image of the time display onto a screen or onto a surface such as an indoor ceiling or wall. The digits are large enough to be easily read, without using glasses, by persons with moderately imperfect vision, so the clocks are convenient for use in their bedrooms. Usually, the timekeeping circuitry has a battery as a backup source for an uninterrupted power supply to keep the clock on time, while the projection light only works when the unit is connected to an A.C. supply. Completely battery-powered portable versions resembling flashlights are also available.

In 1283, a large clock was installed at Dunstable Priory; its location above the rood screen suggests that it was not a water clock.[citation needed] In 1292, Canterbury Cathedral installed a 'great horloge'. Over the next 30 years there are mentions of clocks at a number of ecclesiastical institutions in England, Italy, and France. In 1322, a new clock was installed in Norwich, an expensive replacement for an earlier clock installed in 1273. This had a large (2 metre) astronomical dial with automata and bells. The costs of the installation included the full-time employment of two clockkeepers for two years.[citation needed]
Though no longer our first pick of timepiece thanks to the smart phone, this old-fashioned clock still scores points for form. Measuring 6.25'' H x 2.5'' W x 5'' D, this compact clock’s face is encased in a metal case with a brushed nickel finish and convex glass lens, while its faded dial stays in step with vintage styling. This item is battery operated, but does not emit a loud ticking noise, so you can snooze to your heart's content.
The returned instants from Clock work on a time-scale that ignores leap seconds, as described in Instant. If the implementation wraps a source that provides leap second information, then a mechanism should be used to "smooth" the leap second. The Java Time-Scale mandates the use of UTC-SLS, however clock implementations may choose how accurate they are with the time-scale so long as they document how they work. Implementations are therefore not required to actually perform the UTC-SLS slew or to otherwise be aware of leap seconds.
The invention of the mechanical clock in the 13th century initiated a change in timekeeping methods from continuous processes, such as the motion of the gnomon's shadow on a sundial or the flow of liquid in a water clock, to periodic oscillatory processes, such as the swing of a pendulum or the vibration of a quartz crystal,[3][63] which had the potential for more accuracy. All modern clocks use oscillation.
The right wall-mounted timepiece can be and stylish accent or the focal point of your room's decor. Wall clocks offer an opportunity to reinforce the design of your space, enhance wall décor and add functionality to your room. Showcase them alone or make the clock a stylish addition to a gallery wall. Some designs even allow you to display multiple time zones.

By the time that phone hits the nightstand, you've lost precious sleep time, you've tricked your brain into thinking it's wake-up time instead of dream time, because the glow of the blue light emitted by your phone reduces your body's release of melatonin, the hormone that regulates your sleep cycle. Instead of relaxing, you've stimulated your mind. All of that adds up to poor quality sleep followed by a groggy, foggy, "I don't know why I'm so tired," kind of morning.

The most accurate mechanical timekeeper is the Shortt pendulum clock; it makes use of the movement described above for electric master clock systems. The Shortt pendulum clock consists of two separate clocks, one of which synchronizes the other. The timekeeping element is a pendulum that swings freely, except that once every half minute it receives an impulse from a gently falling lever. This lever is released by an electrical signal transmitted from its slave clock. After the impulse has been sent, a synchronizing signal is transmitted back to the slave clock that ensures that the impulse to the free pendulum will be released exactly a half minute later than the previous impulse. The pendulum swings in a sealed box in which the air is kept at a constant, low pressure. Shortt clocks in observatories are kept in a room, usually a basement, where the temperature remains nearly constant, and under these conditions they can maintain the correct time to within a few thousandths of a second per day.
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This fun desk clock from the popular Buddy family of products by Umbra holds the time aloft, grabbing attention and helping remind you of the importance of your time! Constructed of molded material with a soft-touch finish, the clock features a steel base for stability, bend-resistant clock hands, and an enclosed back. Operates on one AA battery (not included). Designed by Alan Wisniewski and Matt Davis for Umbra - the worldwide leader in innovative, casual, contemporary and affordable design...
At home in the most up-to-date atmospheres, this wall clock combines a Merlot Cherry finish with brushed nickel accents. The brushed nickel-finished pendulum and bezel add to the contemporary styling. The crisp white dial features black bar hour markers and black hour and minute hands. Finished in Merlot Cherry, a very dark maroon finish that is leaning toward black on an injected molded body. Quartz, battery operated movement.

Here at the Strategist, we like to think of ourselves as crazy (in the good way) about the stuff we buy (like pillows), but as much as we’d like to, we can’t try everything. Which is why we have People’s Choice, in which we find the best-reviewed (that’s four-to-five-star reviews and lots of ‘em) products and single out the most convincing. While we’ve tried to find the nicest-sounding alarm clocks and ended up with picks for the best alarm clock and a voice-controlled alarm clock, we wanted to see what other ways to wake up were out there. So we found the best alarm clocks on Amazon, according to hyperenthusiastic reviewers. (Note that reviews have been edited for length and clarity.)
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