GPS week number rollover

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GPS week number rollover
Ticket terminal in Prague, showing August 23 as the date (instead of April 8) after the 2019 GPS week number rollover
DateEvery 1,024 weeks, starting 1999 August 21 00:00

The GPS week number rollover is a phenomenon that happens every 1,024 weeks, which is about 19.6 years. The Global Positioning System (GPS) broadcasts a date, including a week number counter that is stored in only ten binary digits, whose range is therefore 0–1,023. After 1,023, an integer overflow causes the internal value to roll over, changing to zero again. Software that 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.

1999 occurrence[edit]

The first rollover took place midnight (UTC) August 21 to 22, 1999.

NavCen issued an advisory prior to the rollover stating that some devices would not tolerate the rollover.[1] Because of the relatively limited use of GPS during the 1999 rollover, disruption was minor.

2019 occurrence[edit]

The second rollover occurred on the night of April 6 to 7, 2019, when GPS Week 2,047, represented as 1,023 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.


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.[3] Furthermore, the New York City Wireless Network (NYCWiN), a private network for New York City's municipal services,[4] crashed.[5] Other products that were affected by the rollover include cellphones that were sold in 2013 or earlier,[6] certain types of older Vaisala radiosonde groundstations, suspending launches at some stations for up to two weeks,[7] NOAA's weather buoys,[8] many scientific instruments,[9] and consumer GPS navigation devices.[10]

Prior to return to normal standard time from daylight saving time during the morning of November 3, 2019, Apple issued a warning to owners of iPhone and iPad devices sold before 2012 to update or risk losing Internet connectivity.[11]

Some Furuno GPS models had an internal rollover on January 2, 2022. If the equipment was not updated with the latest software version, the equipment's date would no longer be displayed correctly.[12]

Honda and Acura cars manufactured between 2004 and 2012 containing GPS navigation systems incorrectly displayed the year 2022 as 2002, with a time offset by several minutes. This problem was due to an overflow on the GPS epoch.[13][14]

All Porsche models with PCM2.1 are also affected according to bulletin #1904 released by Porsche on December 20, 2019.

2038 occurrence[edit]

The third rollover will occur between November 20 and 21, 2038.[15] This is unrelated to the Year 2038 problem, which will occur in January of that year.

2137 occurrence[edit]

The above rollovers are due to a ten-bit week number; the more recent CNAV protocol, successor to the original NAV protocol, uses thirteen-bit week numbers, which amounts to a 157-year cycle; therefore, using the same epoch of 1980, the first rollover will not be until 2137.[15]

See also[edit]


  1. ^ "Advisory for the August 1999 GPS Week Rollover". Retrieved September 3, 2020.
  2. ^ "The April 2019 Global Positioning System (GPS) Week Number Rollover". Retrieved March 14, 2019.
  3. ^ Gallagher, Sean (April 9, 2019). "Somebody forgot to upgrade: Flights delayed, cancelled by GPS rollover". Ars Technica.
  4. ^ "NYC Wireless Network". NYC Connected Vehicle Project. Archived from the original on July 12, 2021. Retrieved September 11, 2021.
  5. ^ Divis, Dee Ann (October 17, 2019). "GPS Rollover Hamstrings New York City Wireless Network and a Handful of Other Systems". InsideGNSS.
  6. ^ Shekar, Shruti (April 9, 2019). "Telus contacting customers in advance about GPS rollover that may affect some customers". Mobile Syrup.
  7. ^ Cozzens, Tracy (April 9, 2019). "GPS Week Rollover grounds Aussie weather balloons, Boeing planes". GPS World.
  8. ^ "Effects of GPS Rollover on Weather Buoys and C-MAN Stations" (PDF). NOAA.
  9. ^ Butler, Declan (April 3, 2019). "GPS glitch threatens thousands of scientific instruments". Nature. doi:10.1038/d41586-019-01048-2. PMID 32238891. S2CID 132616195.
  10. ^ Vincent, James (March 8, 2019). "Older GPS devices are facing their own mini Y2K bug next month". The Verge. Retrieved August 17, 2019.
  11. ^ "Apple Warns Some iPhone Users: Update your phone or lose internet". WHO-TV. Des Moines, Iowa. October 31, 2019. Retrieved October 31, 2019 – via CNN.
  12. ^ "Furuno GPS recievers [sic] affected by GPS rollover 02.01.2022". Furuno Norge AS. January 5, 2022. Retrieved March 31, 2022.
  13. ^ "Honda Clocks Are Stuck 20 Years In The Past And There Isn't A Fix". Jalopnik. January 6, 2022. Retrieved January 8, 2022.
  14. ^ "Shoddy coding has some Honda cars stuck in the year 2002". Engadget. January 7, 2022. Retrieved January 8, 2022.
  15. ^ a b " GPS Week Number Rollover - April 2019". Retrieved September 3, 2020.