Back in late 1999, hysteria was running high due to concerns over Y2K. Many felt that the arrival of 1/1/2000 would bring a technological catastrophe as computers and other critical electronic systems failed to roll over to the correct date. Although Y2K only ended up causing a few minor bugs, this doesn’t mean that the concern was unfounded. If computer systems aren’t correctly programmed to handle date rollover events, malfunctions can be serious and costly — preemptive fixes leading up to Y2K were estimated at $100 billion in the U.S. alone.

We bring this up because we’re rapidly approaching another pivotal date. This time, it’s related to global positioning systems and other systems that rely on them. The U.S. Department of Homeland Security (DHS) released a memo explaining “the possible effects of the April 6, 2019 GPS Week Number Rollover on Coordinated Universal Time derived from GPS devices.” If you’re not intimately familiar with programming and GPS functionality, the problem is rather complicated, but can be simplified as follows:

  • Many electronic devices derive Coordinated Universal Time (UTC) from GPS in order to display the correct time and date.
  • These GPS systems track the date on a cycle of 1,024 weeks, or 19.7 years. This is called an “epoch.” The first GPS epoch began in January 1980 and ended in August 1999. The second epoch ends on April 6th, 2019.
  • Some devices may not be programmed to handle this change, leading to incorrect date calculation and strange behavior.

If the GPS date signal is inaccurate, various systems’ schedules may be interrupted. An article by FalTech GPS explains the potential impact: “This situation won’t affect a receiver’s ability to navigate and/or calculate precise time, but it has the potential to create week, month and year timestamps that are wildly wrong. Applications which rely on GPS data at that level may be seriously affected.”

This is why the DHS has “strongly encouraged” owners and operators of GPS devices to ensure that their systems are prepared for this rollover. Specifically, the following steps are recommended:

  1. Investigate and understand your systems’ possible dependencies on GPS for obtaining UTC.
  2. Contact the manufacturers of your GPS devices to determine if they’ll be affected by the rollover, and if so, what actions are required.
  3. Ensure your devices’ firmware is up to date.

While the majority of GPS devices will probably have no issues coping with this rollover event, the DHS found some devices that failed. “Tests of some GPS devices revealed that not all manufacturer implementations correctly handle the April 6, 2019 WN rollover.” So, it’s worth keeping an eye out for date-related problems starting on April 6th.

For more information on the GPS Week Number Rollover Event, read the full DHS memo.


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