Issue Summary:

• Older GPS receivers define time using 10 bits to count GPS Week Numbers. This representation can only cover a finite period of 1024 weeks (19.7 year epoch).
  
  
• GPS Time started on Jan 6, 1980
  
  
• The first GPS Time Epoch rollover occurred 1,024 weeks later on August 21, 1999.
  
  
• GPS Time is presently in its second Epoch, which will end on April 6, 2019 (just 4 weeks away).
  
  
• Newer GPS receivers from major manufacturers are likely fully compliant with GPS Interface Control Documents 200/IS-GPS-200 standard and should handle this event OK.
  
  
• Older GPS receivers (>9-10 years old) MAY become unreliable, including providing incorrect time tags which could corrupt navigation data at the system level.
  
  
• The failure is not limited to April 6/7 2019.
  
  
• GPS capabilities in most modern smartphones will likely not be affected.

Government officials have been preparing for the data rollover for several years now, as have many GPS device makers. In April 2018, the Dept. of Homeland Security issued a memo warning "federal, state, local, and private sector organizations" of what could happen now that our society has become so dependent on GPS capabilities:

"Critical Infrastructure (CI) owners and operators and other users who obtain Coordinated Universal Time (UTC) from Global Positioning System (GPS) devices should be aware of the GPS Week Number (WN) rollover events and the possible effect a GPS WN rollover event may have on the reliability of the reported UTC,” the memo said. “A GPS device that conforms to the latest IS-GPS-200 and provides UTC should not be adversely affected. However, tests of some GPS devices revealed that not all manufacturer implementations correctly handle the April 6, 2019 WN rollover."

Bill Malik, Vice President of the multinational cyber security and defense company Trend Micro, this week stated; "I'm not going to be flying on April 6." 

While this rollover previously occurred on Aug. 21, 1999 with little impact, "the effects would be more widespread [today] because so many more systems have integrated GPS into their operations."

"Ports load and unload containers automatically, using GPS to guide the cranes," Malik said. "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."

Recommendations:

If you make use of older GPS receivers, perhaps in your work, in general aviation aircraft, on a boat, etc.., your system may very well be impacted by this issue beginning (but not limited to) April 6/7, 2019.

To ensure that critical infrastructure and other systems reliant on GPS won't be impacted, the Dept. of Homeland Security has these recommendations for operators:

• Investigate and understand possible dependencies on GPS for obtaining UTC
  
  
• Contact the GPS manufacturers to obtain UTC to:
  
  A) Understand the manufacturers’ preparedness for the April 6 2019 rollover
  
  B) Understand the actions required by critical infrastructure and other owners and operators to ensure proper operation through the April 6, 2019 rollover
  
  C) Ensure that the firmware of such devices is up to date