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Some older radio-controlled clocks may adjust for Daylight Saving Time early

March 9, 2013

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Contact: James Burrus

Due to an unexpected technical issue, some older radio controlled clocks may have made the change to Daylight Saving Time (DST) up to a day earlier than intended.

Daylight Saving Time begins on Sunday March 10, 2013, at 2:00 am local time. At that time, clocks should move ahead one hour (to 3:00 am local time) in areas observing DST. Radio-controlled clocks and watches (colloquially known as “atomic clocks”) receiving time signals from the National Institute of Standards and Technology’s radio station WWVB should make this time change automatically. However, this year some older versions of radio-controlled clocks may have made the change early.

The WWVB time broadcast includes “warning” information that DST changes will be coming in the next day. Some older radio-controlled clocks may not have correctly interpreted this advance notice and instead made the switch to DST too early. All radio-controlled clocks, including those that may have made the DST switch early, should be working properly by the time DST officially begins on Sunday morning.

NIST regrets any inconvenience caused by the error.

For more information about NIST radio station WWVB and radio-controlled clocks, please see: http://www.nist.gov/pml/div688/grp40/wwvb.cfm