NIST radio station WWVB continuously broadcasts time and frequency information on its 60 kHz carrier frequency from Fort Collins, Colorado. WWVB provides coverage to the United States, Mexico, and Canada, providing a convenient reference for many consumer electronic products such as desk clocks, wall clocks, and wrist watches. The stable ground wave signals are also widely used as a reference for frequency calibrations.

NIST continously monitors the WWVB signals from Boulder, Colorado and compares the phase of the received signal to the national frequency standard maintained by NIST. Values are published in the archive that represent the daily accumulated phase shift for WWVB relative to the NIST frequency standard.

To view archived WWVB phase data, select the month and year and then click the "Get data" button. Since new data are added to the archive monthly, last month is selected by default.