Re: [gpsd-dev] gpsd rolls back to 1999

[Hal Murray]

> I have a Surefire MTK-3301 , which has been running well for over 6 years.
> Noticed today that ntp was reporting 1999 . 

GPS has a 10 bit filed for the week number.  That works out to be about 20 
years.
  https://en.wikipedia.org/wiki/GPS_Week_Number_Rollover
Or search for WNRO.

It rolled over recently.  But that doesn't mean your GPS unit will start 
screwing up.  The firmware can compare the date from GPS with the build date 
of the firmware.  That gives the firmware a lifetime of 20 years starting at 
firmware build time.  Any dates before the build date get bumped up by 1024 
weeks.  You may have to bump by multiple steps of 1024 weeks.  (Loop until GPS 
time > build-time.)


Software like GPSD and NTPD can do the same thing.  That gives you a lifetime 
of 20 years after the software build time.  If you can rebuild, the 20 year 
window keeps moving.

If you are using ntpd, you can fudge the time.


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