The 9 Best Atomic Clocks
Updated by · How we research
Nine self-setting wall, alarm and projection clocks compared for reception, readability and power. The La Crosse WT-3129B is the plainest to hang and forget. When users buy our independently chosen editorial selections, we may earn commissions to help fund the Wiki.
No clock sold for the home holds an atomic oscillator. These are quartz clocks with a small radio that listens each night for the time signal NIST broadcasts from Fort Collins, Colorado, so they set themselves and follow daylight saving time. They work across the mainland U.S., though metal roofs and basements can block reception. Wall, desk, alarm and projection styles are here.
From the manual
- Set the zone and daylight saving switches before fitting batteries; the hands then park at 12 and may need five nights to set. setup sheet, p. 2
- Any of its three slots takes an AA: one cell is rated for up to two years, three for up to six. setup sheet, p. 3
- Hands that spin, jump or stick usually mean a weak or wrong battery, its top warranty issue, so La Crosse asks for fresh name-brand alkalines. pp. 2, 4
- No booster antenna works with it, and opening the clock or its movement voids the warranty. p. 4
From the manual
- Batteries go into the outdoor sensor first, then the clock; mount the sensor upright in shade, ideally under an eave or deck rail. pp. 1, 5
- The sensor reaches over 300 feet in open air, but La Crosse says to halve that for each wall, window or tree in the way. p. 6, FAQ p. 7
- The moon phase is calculated from the year and date you enter, not sent by the time signal. p. 4
- If the outdoor reading shows dashes, bring the sensor in, pull both battery sets, press a button 20 times and wait 15 minutes before refitting. p. 6
From the manual
- Don't turn the hands yourself while it hunts for the signal; it parks at 12 and can take up to five nights to set. p. 1
- La Crosse suggests a fresh battery every two years, and warns that big offices, schools and hospitals may lack signal in some rooms. p. 2
- Holding the WAVE button for three seconds starts a signal search on demand, which takes about three to eight minutes. p. 3
- Opening the clock or its movement voids the one-year warranty. p. 4
From the manual
- It runs on its 5-volt adapter; the three AAA cells only hold the time and date through a power cut. p. 2, FAQ p. 11
- La Crosse says it must stay on the power cord to receive outdoor sensor updates. FAQ, p. 7
- The projector arm tilts toward a wall or the ceiling, and a wheel on its back turns the image through 270 degrees. p. 6
- Auto Dim drops the backlight to its dimmest lit setting between hours you choose, then brings it back up. p. 4, FAQ p. 7
From the manual
- One AA in the movement lasts at least a year; adding a cell to each side compartment stretches that to five years or more. p. 3
- After the first signal it shows Pacific time; hold your zone button until the hands start to spin, and they move to your hour. p. 2
- It isn't waterproof: La Crosse wants a dry spot sheltered from sun and rain, between about -10 and 131 degrees F. FAQ, p. 5
- You can set the time by hand only for about two minutes after the batteries go in. FAQ, p. 3
From the manual
- It runs on a 5-volt adapter, with two AA cells as an optional backup, and waits two hours after they go in before searching. p. 1
- Once set, it checks the signal again only after midnight; holding MINUS for three seconds forces a search. p. 2
- The alarm builds in volume, rings for two minutes and stops; any button except SNOOZE silences it for a day. p. 4
- If a new clock's screen looks garbled, peel off the printed scratch-guard film over the display. FAQ, p. 5
Editor's Notes
November 4, 2026, by Ezvid Wiki Editors:
We read La Crosse's setup guides and FAQ sheets for its six picks and added notes from them under each one. The guide now gets the Hawaii and Arizona daylight saving advice right, drops an unsourced line about Alaska and Hawaii reception and gives La Crosse's restart steps; the patio clock's five-year battery life now notes it needs three cells. La Crosse lists the WT-3129B, WT-3143A, 513-1417CH, 616-41667 and 513-1419BL as retired, with newer versions of the last three, so those picks get another look in a later update.
October 23, 2026, by Ezvid Wiki Editors:
The La Crosse WT-3129B takes over the top spot. It's the plainest way to own a clock that sets itself: one battery, a clear dial, and nothing to adjust after you pick a time zone. Most of the old list had disappeared. The Forestime Digital, Marathon CL030054B, Hito HT1801, Oregon Scientific HiGlo, Hito htc8376 and Marathon Jumbo CL030025 are no longer available. The La Crosse Technology 308-141 has turned into a color weather station, and the Britta Products Franklin CL-1 was down to its last unit, so both went too.
The Sharp Brushed Silver Analog and La Crosse WT-3143A stay. New picks follow what readers search for: digital clocks that show the outdoor temperature, a bedside alarm, a projection clock, a covered-patio clock and a calendar clock for memory care.
Our evidence was NIST's own guidance on the WWVB signal, its reception tips and outage notices, La Crosse's product pages, the recurring reception complaints in owner feedback, and a recall search. We found no published side-by-side reception tests of home radio-controlled clocks, so reception, which depends on where you live, remains the main unknown.
Earlier notes
November 28, 2020, by Karen Bennett:
The addition of the Sharp Analog brings another analog model to the list. It sports bold black numbers and hands against a white background, to provide the contrast needed for easy viewing. This silent wall clock incorporates a sweeping hand that does not tick, and it’s accurate to within one second. You’ll appreciate not needing to change it manually to adjust for daylight savings time, as it takes care of that automatically for you. The sleek brushed metal frame will add to the decor nicely of any area of your home or office. The Hito HT1801 also comes on board, which is a good choice for households where family members need to be awoken at different times, as it features two alarms. It’s equipped with what you’ll need for either wall mounting or placement on a nightstand. It can be set up in a few quick steps, and shows the day of the week, indoor temperature and humidity, and the time in large numbers. This 6.3-inch model replaces the larger, 9-1/2-inch Hito HT1602, which is unavailable at this time.
For those who enjoy the convenience and the novelty of a projection clock, the newly added Oregon Scientific HiGlo is a viable option. It can be projected onto the ceiling or a wall, although note that the beam’s angle is not adjustable. You can set it to display the current day of the week in English, Spanish, or French. It’s got a built-in thermometer and a crescendo alarm with a snooze function. It replaces the Oregon Scientific Proji, another projection clock, which is unavailable at this time. We moved the La Crosse Technology 308-141 into a more prominent position on the list, as this full-featured weather station with a sensor has a lot to offer. It shows the temperature, humidity, and mold risk for your indoor and outdoor environments, as well as images to indicate whether sunny skies or cloudy ones are in store. Both the numbers and graphics are brightly colored, for an attractive screen that’s easy to read with just a quick glance.
May 17, 2019:
In addition to helping keep you on time, atomic clocks can boast an array of other features that make planning and going about your day easier, and we wanted to select models that show that. The Hito HT1602 lets you set two alarms, so you can set one for your wakeup time and another for an afternoon reminder. The Marathon CL030054B warns you when it's too hot to step outside, so you don't have to learn the hard way by going outdoors and potentially suffering a heat stroke. The X-Sense Weather Station even shows the local weather forecast, helping you know when to pack an umbrella or sunscreen. Your clock isn't much good if you can't see it well, so visibility was important, too. The Oregon Scientific Proji both projects the time onto the ceiling, as well as shows it on its face. Meanwhile, the Britta Products Franklin CL-1 has a liquid crystal display that's easy to see in daylight. Both the Hito htc8376 and the Hito HT1602 have good back lights for nighttime visibility. We considered both large, stationary models and compact portable ones, too, so the analog-style La Crosse Wall WT-3143A and the stylish Marathon Jumbo CL030025 caught our attention for nice home or office choices. For timekeepers on the go, the Hito htc8376 is a nice compact choice.
Special Honors
NIST Time The National Institute of Standards and Technology runs time.gov, a free page that shows official U.S. time for each zone, drawn from the same atomic clocks behind the WWVB signal. It's a quick way to check whether a new radio clock has synced, and it needs nothing more than a web browser. time.gov
What Makes A Clock Atomic
The signal is in universal time, so the clock adds the time zone you choose, and a flag in the code tells it when daylight saving time starts and ends.
Strictly speaking, none of these clocks is atomic. NIST, which runs the U.S. time signal, says the name isn't really true: a real atomic clock keeps time with atoms, while a home clock is a quartz clock with a small radio that receives a signal derived from one. That signal comes from station WWVB near Fort Collins, Colorado, on 60 kilohertz.
The real thing has a long history. NIST built the first atomic clock in 1949 using ammonia, and the first cesium clock followed at Britain's National Physical Laboratory in 1955 (NIST history). NIST-F2, launched in 2014, would neither gain nor lose a second in about 300 million years (NIST).
A home clock borrows that accuracy once a day. WWVB sends one bit per second, so a full time code takes a minute (NIST), and most clocks try in the middle of the night, when the signal is strongest (NIST FAQ). Between syncs the quartz movement keeps time on its own. The signal is in universal time, so the clock adds the time zone you choose, and a flag in the code tells it when daylight saving time starts and ends.
How close is close enough? Michael Lombardi, a NIST time researcher, took that up in the British Horological Institute's Horological Journal in March 2010: a radio clock "should always be accurate to within one second of UTC," as long as it syncs at least every other day and its quartz is decent (Lombardi).
Getting The Signal, And Keeping It
WWVB should work in most of North America, and it covers the most ground at night. NIST's coverage maps leave out Alaska, though it has heard several reports from Alaska of clocks working fine (NIST). In Hawaii, the first hurdle is the setting: NIST has heard from buyers there whose clocks can't select the Hawaiian zone. WWVB clocks don't work in Europe or Asia, which run their own time stations.
Placement decides most problems. NIST suggests keeping the clock a meter or two from computer monitors and putting it on or near a wall or window that faces Colorado; La Crosse asks for 6 feet from TVs, microwaves, routers and cordless phones (La Crosse). Turn a desk clock 90 degrees if it won't sync. Metal roofs, steel siding and mobile homes can block the signal, and La Crosse warns that large offices, schools and hospitals may not get it in every room. A new clock may need a night or more; La Crosse manuals allow up to five nights in poor conditions. Fresh alkaline batteries help. If a clock still won't set, La Crosse's restart is to take the batteries out for 15 minutes and press a button 20 times before putting them back.
The station itself goes quiet now and then for maintenance; NIST posts the dates on its outage page. A clock just keeps running on quartz and catches up the next night. If a clock shows the wrong hour, check the time zone setting first. In Hawaii and most of Arizona, turn daylight saving off; the Navajo Nation in Arizona does observe it (NIST).
Choosing A Style, And Battery Safety
Analog wall clocks are the simplest: most run a long time on one AA cell and have nothing to set but the zone. Digital models add the date and often an outdoor temperature from a wireless sensor, which needs its own batteries and a shaded spot outside. If the outdoor reading goes blank, move the sensor closer or out from behind metal, and replace both sets of batteries together. Check the zone list too: La Crosse makes no analog clock with more than four zones, Eastern through Pacific (La Crosse FAQ), while its digital models here add Alaska, Hawaii and Atlantic time.
Alarm and projection clocks usually run from a wall adapter with batteries as backup. Use the adapter that came with the clock.
Watch for coin batteries. In 2025 the CPSC announced a recall of Leon Rading digital wall clocks because their remote held a lithium coin cell that a child could reach (CPSC). Swallowed coin cells can cause serious internal burns. The La Crosse clocks on this list take AA or AAA cells, but some plug-in alarm clocks keep their settings on a small built-in button cell, so keep battery doors closed in a child's room.
How we researched this
We compared 27 self-setting clocks, including every clock from the previous list. For the six La Crosse picks we read the maker's own documents: the WT-3129B setup sheet and FAQ, the WT-3143A instruction manual, the 513-1417CH and 513-1419BL quick-start manuals, the 616-41667 setup guide and the 404-18027 setup sheet, while no maker manual turned up for the two Sharp clocks or the DreamSky. NIST's WWVB help pages and outage log, plus Michael Lombardi's 2010 Horological Journal article on radio-clock accuracy, shaped the buyer's guide. A search of CPSC recall notices found nothing for La Crosse, Sharp or DreamSky clocks; the one clock recall that turned up, Leon Rading's 2025 wall clock, isn't on this list.
Sources (12)
- NIST: Help with WWVB radio-controlled clocks
- NIST: NIST radio broadcasts FAQ
- NIST: WWVB station outages
- NIST: A brief history of atomic time
- NIST: NIST-F2 atomic clock launch
- CPSC: Leon Rading digital wall clock recall (2025)
- La Crosse Technology: WT-3129B
- NIST: time.gov
- Michael A. Lombardi (NIST): How accurate is a radio controlled clock? Horological Journal, March 2010
- NIST: Local time FAQs (daylight saving time)
- La Crosse Technology: WT-3143A instruction manual (PDF)
- La Crosse Technology: WT-3129B/WT-3129S FAQ (PDF)
Frequently asked questions
Is an atomic clock really atomic?
No. NIST says home atomic clocks are quartz clocks with a radio receiver. They set themselves from the WWVB signal, which comes from real atomic clocks in Colorado.
Why won't my atomic clock set itself?
Usually it's placement or batteries. Move it away from TVs and routers, put it near a window facing Colorado, fit fresh batteries and leave it overnight. Metal roofs and steel siding can block the signal.
Why doesn't my atomic clock show the outside temperature?
The outdoor reading comes from a separate wireless sensor. Check its batteries, bring it closer to the clock, and keep it out from behind metal. Some clocks need a restart to pair with the sensor again.
Do atomic clocks work in Alaska, Hawaii or Europe?
WWVB covers most of North America. Alaska is outside NIST's coverage maps, yet NIST has heard from owners there whose clocks work. A clock there or in Hawaii needs that time zone in its settings. WWVB clocks don't work in Europe or Asia, which use other stations.
How accurate is an atomic wall clock?
It should stay within a second of official time as long as it syncs at least every other day. Between syncs it runs on quartz, which NIST says usually drifts a second a day or less, so a few missed nights cost only seconds.
Can I hang an atomic clock outside?
Only one built for it, and only under cover. Most wall clocks are for indoor use; an outdoor temperature sensor is a separate part designed to sit outside.
