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Daylight Savings Time Fail

Ed Grochowski

Posted 3-10-2014

The Buggy Radio-Controlled Clock

A Technology Challenge

The start of Daylight Savings Time in the United States always poses a challenge for my radio-controlled clocks.

I own two such clocks. Both failed to adjust automatically to the start of Daylight Savings Time last Sunday. These clocks were manufactured in 2004, before the current DST dates were adopted, and so any pre-programmed dates are wrong. In theory, the WWVB radio signal should inform the clocks when to switch to Daylight Savings Time, but this feature had not been adequately validated by the manufacturers.


On the clock in the photo, I manually pressed the synchronize button to work around the off-by-one error in the clock's firmware (the automatic DST adjustment occurs one day too late). On the other clock, I previously had turned off automatic DST adjustment (because it was buggy), and so I turned it back on.

That fixed the immediate problem of the clocks telling the wrong time for most days. There is still the long-term problem that I own two clocks that tell the wrong time on two days of the year.

Foreshadowing the Internet of Things

Adjusting the radio-controlled clocks has become a yearly ritual in my household, just like conventional clocks. By now, I regard the manufacturers' claims of "World's Most Accurate Clock" and "Never Needs Setting" as reflecting the naive optimism of someone who has never encountered a computer.