Y2K All Over Again

Panic or unease was held by many almost 20 years ago, in the fall of 1999, because of the calendar rollover of year 2000. Some thought this event would cause catastrophic issues. Much like the Y2K bug of 20 years ago, April 6th, 2019 brings the potential for global issues, with a similar calendar-related issue potentially causing problems for some GPS receivers.

The current calendar rollover, referred to as GPS Week Rollover, is very similar to the Y2K rollover. This issue is due to the way navigation signals work. In navigation systems, weeks are numbered from 0 to 1023. Week 0 began Sunday. August 22, 1999. Week 1023 begins on March 31, 2019. At 1 second after 11:59:59pm on Saturday, April 6, the GPS Week number resets to 0. Updated GPS hardware and software will interpret this as Sunday, April 7, 2019 but other systems might believe it is Sunday, August 22, 1999 or even worse, January 6, 1980 (the beginning of the first cycle of weeks used by navigation systems).

The uninformed might say “What’s the big deal if my GPS has the wrong date?” The big deal is that global positioning uses time and date in order to calculate location and changes in location. Errors in GPS navigation can tell aircraft, ships or cars that they’re miles from where they actually are. If confused by this change, the location data could even relay that they are in the Gulf of Guinea off the coast of Nigeria, the “zero point” for GPS systems.

Consumer-grade GPS units used in cars or for outdoor sports made after 2010 or that have received firmware updates in the last 10-15 year should be fine. GPS device manufacturers have been preparing for this event for some time, since it is the second time it’s happened (i.e. August 21/22, 1999).

For most consumers, however, the real concerns are not about GPS systems themselves, but the systems they rely on, which may in turn rely on GPS.

Experts maintain that most modern GPS receivers will be okay because the navigation signals used utilize UTC (Universal Time Coordinated), which is not dependent on the week calculation.  However, the Department of Homeland Security (DHS) has been in regular communications with vendors that provide GPS equipment used in the critical infrastructure sector which includes access and industrial control, banking, communication systems, and power grid systems. DHS is involved with research to develop “alternate PNT (position, navigation and timing) capabilities to augment GPS.” This will not only prevent issues such as the GPS Week Rollover but protect our nation’s critical infrastructure from GPS systems being hacked, jammed or spoofed.

Critical industries have responded to the issue on the web and via social media, but not in a direct “announcement” sort of way – unfortunately.


Former communications network engineer, Carl “Bear” Bussjaeger, tweeted

“Networks don’t time off GPS. They time off internal/master station clocks. Those clocks periodically synchronize off GPS.”

After another current engineer argued that his company had switched to GPS-only clocks, Bussjaeger responded by tweeting

“Sure, we had a similar setup. But the clocks free-run fine for days if GPS is cut.”

Air Travel

The consensus is that most commercial airlines will have no issues with the date rollover. The primary concern is related to smaller, privately-owned aircraft that may have older GPS equipment that has not be updated. No airline or federal aviation regulators have commented directly on concerns. However, several companies that manufacture GPS devices used by private pilots have posted updates regarding their products’ status regarding this issue.

Power Grid

The United States Naval Observatory maintains the Master Clock, Network Time Protocol (NTP) servers, web-based time synchronization, and GPS timing products and services. In a short online presentation, published in 2017, the U. S. Naval Observatory recommended that all receiver owners contact the receiver manufacturer to see how their receivers may be impacted by this upcoming event.  But once again, no public declaration of “everything will be fine” can be found.

During the fall that preceded the Y2K transition there were those declaring a global catastrophe was upon us, while others were of the opposite opinion that nothing would happen. As it turned out, nothing of note did happen, other than a few VCRs whose timers were no longer usable.

I suppose we’ll have to “wait and see” what happens this time. If nothing else, it serves as a reminder to back up your computer, make sure you have emergency supplies at home, and … maybe don’t plan any long airline flights that extend from Saturday, April 5, 2019 into the next day.

Author: Todd Williams, Help Desk Supervisor


@BearBussjaeger. “No, we aren’t. Networks don’t time off GPS. They time off internal/master station clocks. Those clocks periodically synchronize off GPS. Been there, done that.” Twitter, March 9, 2019 10:43am, twitter.com/BearBussjaeger/status/1104452729412485120.

Kingsley-Hughes, Adrian. “Some GPS receivers may malfunction on or after April 6.” ZD Net, CBS Interactive, 12 Feb. 2019, www.zdnet.com/article/some-gps-receivers-may-malfunction-on-or-after-april-6/.

Powers, Edward. “Powers – GPS Week Roll Over Issue.” U.S. Naval Observatory, 26 Sept. 2017.

United States, Department of Homeland Security, Science and Technology Directorate. “GPS Vulnerabilities for Critical Infrastructure.” GPS Vulnerabilities for Critical Infrastructure, 13 Apr. 2016. www.dhs.gov/sites/default/files/publications/GPS Vulnerabilities for Critical Infrastructure Fact Sheet.pdf.

Wagenseil, Paul. “GPS Flaw: Security Expert Says He Won’t Fly April 6.” Tom’s Guide, 11 Mar. 2019, www.tomsguide.com/us/gps-mini-y2k-rsa2019,news-29583.html.