Do you know where you’ll be on April 6, 2019? If you heavily rely on GPS, you may not be able to determine where you are when that date rolls around. That’s because GPS navigation technology was originally built with a short-sighted timekeeping system that will reset next month and has the potential to cause chaos.

When the Y2K bug threatened to throw global computer systems out of whack at the turn of the millennium, it set off panic and everyone waited for our newly connected world to crumble at the stroke of midnight. When all was said and done, the hype was overblown and the errors that did occur had a relatively minor impact. That’s probably why a similar flaw in older GPS systems has flown under the radar—we simply refuse to get fooled again.

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GPS was originally designed to timestamp signals using a system that counts weeks using a 10-digit field that tops out at 1024 weeks(~19.7 years). It expresses the time of a signal sent by satellite in weeks and seconds into the week. For a few reasons, a GPS receiver on the ground has to take that signal and calculate the current date as part of the processes it uses to determine location. Once that ten digit field in legacy GPS devices fills up it resets to zero, and that could cause problems.

The U.S. Naval Observatory released a short FAQ on the issue in 2017 and warned that the GPS receiver’s month/year conversion could fail and that incorrect time tags could “corrupt navigation data at the system level.” A recent memo from the U.S. Department of Homeland Security explained that “a nanosecond error in GPS Time can equate to one foot of position (ranging) error.” Of course, an error of 19.7 years has the potential to make the navigation data useless.

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How much fear should this knowledge inject into your daily life over the next month? On a scale of one-to-ten, I’m gonna give a solid two. One reason to chill out is that we’ve been through this before. On Aug. 21, 1999, the GPS counters reset with little disruption to daily life. But GPS wasn’t as ubiquitous back then as it is today. Still, here in the second Epoch of GPS we’ve been anticipating the rollover and modern devices manufactured after 2010 are largely designed with a 13-bit week counter that only needs to roll over every 157 years.

If you’re more of the better safe than sorry type of person, then I’ll direct you to the comments Trend Micro vice president Bill Malik gave to Tom’s Guide. Malik said that he won’t be personally flying that day and he foresees other potential safety issues. “Ports load and unload containers automatically, using GPS to guide the cranes,” he explained. “Public-safety systems incorporate GPS systems, as do traffic-monitoring systems for bridges. Twenty years ago these links were primitive. Now they are embedded. So any impact now will be substantially greater.”

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If the primary way you interact with GPS systems comes from your smartphone, you’re probably all up to date. If you utilize older GPS systems that do not meet IS-GPS-200 standards, DHS recommends you contact the manufacturer with questions.

Again if cargo ships crash into docks and airplanes fly into mountains on April 6th, don’t say we didn’t warn you.

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[Tom’s Guide, DHS, GPS.gov]