GPS Week Number Rollover

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GPS Week Number Rollover
Jizdenkovy terminal praha gps rollover.jpg
Ticket terminal in Prague
ParticipantsGPS users

The Global Positioning System (GPS) Week Number Rollover is a phenomenon that happens every 1024 weeks, which is 19.7 years. The Global Positioning system broadcasts a date, including a weekly counter which is stored in only ten binary digits. The range is therefore 0–1023. After 1023 the internal value "rolls over", changing to zero again. Software which is not coded to anticipate the rollover to zero may stop working or could be moved back in time by 20 or 40 years. GPS is not only used for positioning, but also for accurate time. Time is used to accurately synchronize payment operations, broadcasters, and mobile operators.[1]

The first rollover took place midnight (UTC) August 21 to August 22, 1999, when GPS Week 1023 advanced and rolled over to 0 within the counter.

The second rollover occurred on the night of April 6 to April 7, 2019, when GPS Week 2047, represented as 1023 in the counter, advanced and rolled over to 0 within the counter.[2] The United States Department of Homeland Security, the International Civil Aviation Organization, and others issued a warning about this event.[1][3]


Due to relatively limited commercial and consumer use of GPS during the 1999 rollover, disruption was minor.

Products known to have been affected by the 2019 rollover include Honeywell's flight management and navigation software that caused delays for a KLM flight and cancellations for numerous flights in China because the technicians failed to patch the software.[4] Other products that were affected by the rollover include cellphones that were sold in 2013 or earlier,[5] Australian Bureau of Meteorology's weather balloons,[6] NOAA's weather buoys,[7] , many scientific instruments[8] and consumer gps navigation devices [9].


  1. ^ a b "Již příští měsíc nastane rollover: Přestane fungovat celosvětově systém GPS?". (in Czech). Retrieved 2019-03-14.
  2. ^ "The April 2019 Global Positioning System (GPS) Week Number Rollover". Retrieved 2019-03-14.
  3. ^ Čížek, Jakub. "Blíží se GPS Week Number Rollover Event. Staré přijímače mohou přestat fungovat". (in Czech). Retrieved 2019-03-14.
  4. ^ Gallagher, Sean (2019-04-09). "Somebody forgot to upgrade: Flights delayed, cancelled by GPS rollover". Ars Technica.
  5. ^ Shekar, Shruti (2019-04-09). "Telus contacting customers in advance about GPS rollover that may affect some customers". Mobile Syrup.
  6. ^ Cozzens, Tracy (2019-04-09). "GPS Week Rollover grounds Aussie weather balloons, Boeing planes". GPS World.
  7. ^ "Effects of GPS Rollover on Weather Buoys and C-MAN Stations" (PDF). NOAA.
  8. ^ Butler, Declan (2019-04-03). "GPS glitch threatens thousands of scientific instruments". Nature.
  9. ^ Vincent, James (2019-03-08). "Older GPS devices are facing their own mini Y2K bug next month". The Verge. Retrieved 2019-08-17.