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Features:

• Absolute time and date accuracy
• WWVB radio controlled time and date
• Selection of 24 time zones
• US time zones display with three characters (ATL, EST, CST, MST, PST, ALA, HAW)
• Day, month, date display
• Signal reception indicator
• Manual transmission seeking function
• Plastic case
• Water resistant
• Metal/plastic band
• Stainless steel butterfly clasp
• Battery-saving "OFF" function
• Low battery indicator
• Powered by 3V lithium battery (included), expected lifetime of three years

Dimensions:

• Case: 1-11/16" x 1-9/16" x 1/2"
• LCD: 1/2" x 13/16"
• Time display: 3/16"
• Band Length: 6-1/4" x 13/16"
• Fits wrists up to 8-3/4" (222 mm)
• Removable links to adjust size down in 3/8" (10 mm) increments (20 total links)
• Additional links to lengthen band available

Radio-controlled Time:

The NIST (National Institute of Standards and Technology-Time and Frequency Divisions) maintains a radio station, WWVB, in Ft. Collins, Colorado. The WWVB radio station derives its signal from the NIST Atomic clock in Boulder, Colorado. A team of atomic physicists is continually measuring every second, of every day, to an accuracy of ten billionths of a second per day. These physicists have created an international standard, measuring a second as 9,192,631,770 vibrations of a Cesium-133 atom in a vacuum.

WWVB (the station’s identification just like any other radio station) continuously broadcasts time and frequency signals at 60 kHz. The carrier frequency provides a stable frequency reference traceable to the national standard. There are no voice announcements on the station, but a time code is synchronized with the 60 kHz carrier and is broadcast continuously at a rate of 1 bit per second using pulse width modulation. The time code contains the year, day of year, hour, minute, second, and flags that indicate the status of Daylight Saving Time, leap years, and leap seconds.

The LaCrosse Technology WT-961B Atomic  Watch:

Our La Crosse radio-controlled atomic watch maintains its incredible accuracy by automatically tuning into the WWVB radio signal.

The Atomic Watch contains a small but highly powerful antenna, specifically tuned for optimal reception of the 60 kHz time signal. The signal received on the antenna is demodulated by a tiny onboard receiver, which sends the information to the watch's ultra-low-power CMOS microprocessor for decoding. Once your watch has automatically set its time for the first time, it ensures continuing accuracy by automatically tuning into the WWVB radio signal once per day after midnight. As long as your wristwatch is kept within transmitter range, your Atomic Watch will continue to display the absolutely precise time, even performing automatically the adjustment for summer time/winter time changeovers. Should you move your watch out of transmitter range for an extended period of time, your Atomic Watch will still continue to operate as a highly accurate quartz controlled clock. Upon re-entering the transmitter range, your watch will correct itself again to the precise WWVB time signal.