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GPS Week Number to Rollover


GPS timing is used in military and civilian applications around the world every day.  Due to its critical nature, the GPS community has established and posted guidelines, Interface Specification GPS-200, (online at for receiver manufacturers to ensure continued capability. 

Users should be aware of the upcoming GPS Week Number rollover as it may impact receivers that are not manufactured in compliance with IS-GPS-200 specifications. 


The GPS Week Number count began at approximately midnight on the evening of Jan. 5, 1980/morning of Jan. 6, 1980.  Since that time, the count has been incremented by 1 each week and years later broadcast as part of the GPS message.  One of the GPS week number fields in the legacy navigation message counts from zero to 1023 weeks.  At the completion of every 1024 GPS weeks the field rolls from 1023 to zero and starts counting again.  The first occurrence was on the evening of Aug. 21, 1999 and the message field rolled to zero at midnight GPS Time.  The next similar GPS Week Number rollover occurs on April 6, 2019.


“We appreciate the 4 billion people around the world who use GPS signals on a daily basis, which is why we are transparent in providing detailed guidance on use for compatibility,” said Lt. Col. Stephen Toth, 2nd Space Operations Squadron commander.


Any users who have unanticipated operating issues should contact their respective manufacturers for assistance to troubleshoot the issues.

Additionally the U.S. Coast Guard Navigation Center provides information and services to civil GPS users.  They can be contacted at 703-313-5900 or online at

For more information about GPS, check out the factsheet at   For more information about the 2nd Space Operations Squadron see their factsheet at:

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