Why Your GPS Devices Could Go Haywire Today

(Bloomberg) -- Meet the Y2K-bug’s little brother.

Thanks to a quirk in how Global Positioning Systems keep track of time, some devices are due to have their calendars reset at 7:59 p.m. EDT on Saturday. This echoes the hysteria -- mostly overhyped -- over global computers systems that gripped the world when the calendar was about to click over from 1999 to 2000.

Fortunately, the glitch only affects older GPS systems or ones that haven’t been updated, and the U.S. Department of Homeland Security says it isn’t expecting wide-scale disruptions. But they’ve still been warning that utilities, financial systems, airlines and telecommunication systems could be affected by the problem.

“Anyone who relies on precision timing to do business should be aware there could be some impacts,” said Bob Kolasky, director of the department’s Cybersecurity and Infrastructure Security Agency’s National Risk Management Center. “It’s a pretty broad flaw.”

GPS Time: 1024 Weeks

The issue is caused by the “1024 week number rollover.” GPS systems keep track of time by counting weeks, but only have enough data to keep track of 1,024 of them before they reset to Jan. 6, 1980, when the system first went online.

The last time that happened was in August 1999 when GPS was used a lot less for everything from flying planes to mapping the best driving routes to locating lost pets.

The next reset occurs tonight.

Navigation technology manufacturer TomTom NV told users on its website that “there’s no need to worry” if you frequently update your device, but said those who don’t may find “navigation impossible” among other problems.

Little Worry

Garmin LTD said its testing has shown the “vast majority” of its GPS devices will handle the rollover without issue, and those that are affected will see an incorrect date and time displayed but “the positioning accuracy will not be affected.”

But other industries that rely on precise time could see an impact.

Edward Powers, the GPS Operations Division Chief for the U.S. Naval Observatory, warned in a 2017 presentation that the rollover could lead to corrupted data and system failures, with problems occurring beyond April 6.

“A nanosecond error in GPS Time can equate to one foot of position (ranging) error,” the Cybersecurity and Infrastructure Security Agency, which is part of DHS, said in a memo warning about the problem.

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