What Time is It? FAQs

NIST continually broadcasts the time using shortwave radio signals from two radio stations:

• WWV near Ft. Collins, Colorado broadcasts on 2.5, 5, 10, 15 and 20 MHz
• WWVH in Kauai, Hawaii broadcasts on 2.5, 5, 10 and 15 MHz

The announcement of the time occurs at the top of each minute and states Coordinated Universal Time (UTC) so it will be necessary to adjust the hour to your local time zone.

For more information about the stations, see the Time and Frequency Radio Broadcast section.

There are two telephone numbers that allow you to listen to NIST time:

• 303-499-7111 (Colorado)
• 808-335-4363 (Kauai, Hawaii)

Please note that these are not toll-free numbers. Calls from outside the local area may be subject to long-distance charges.

When calling these numbers, you will hear the same audio that is broadcast by WWV and WWVH, respectively. Note: The use of cellular phones can add a small delay to the broadcast.

There are other local time telephone services in operation. These services are not affiliated with NIST.

The current time is shown on the Internet at https://www.time.gov/ - it synchronizes with NIST every ten minutes. There is an accuracy statement based on a measurement of the round-trip network delay. This delay is measured using your computer clock as a timer each time synchronization is made. The site provides a time-of-day service, and it should not be used to measure frequency or time interval, nor should it be used to establish traceability to NIST.

NIST has considered streaming the audio from WWV/WWVH via the Internet, but because of audio buffering, the time announcement could be several seconds off and would vary for different users. However, the idea is still under consideration.

A computer can be synchronized to NIST via the Internet using our Internet Time Service (ITS) or via a telephone line (through a modem) using our Automated Computer Time Service (ACTS). Several computer operating systems have an option to automatically synchronize the computer clock to NIST time servers. Double-clicking the desktop clock should lead to the options available.

There are many commercial manufacturers who make clocks that receive time signals from NIST radio station WWVB. These are sometimes marketed as "atomic clocks", but we recommend that they be referred to as "radio-controlled clocks". The broadcast station is located near Ft. Collins, Colorado and it continuously broadcasts a time code on a carrier frequency of 60 kHz. These clocks and watches typically synchronize overnight and keep time between synchronizations using an internal quartz crystal oscillator. The WWVB broadcast covers most of the continental United States during the daytime hours, and the coverage area increases at night.

For more information, see the section on NIST radio broadcasts,

Some of the more common problems include incorrectly setting your local time zone on the clock, batteries that need to be replaced, and interference from other electrical devices such as refrigerators and computer monitors. Detailed information about radio-controlled clocks and troubleshooting tips are available on the NIST web page describing WWVB radio-controlled clocks. We include links to manufacturers for additional technical support on their products.