[time-nuts] Incorrect date on Thunderbolt

[Hal Murray]

keith.brandt at gmail.com said:
> I pulled my Thunderbolt out of mothballs this week. It initialized and
> started tracking satellites very nicely, but the date is showing  '16Nov00'.
> The day has incremented at UTC midnight the past 2 days and  the time is
> accurate.

The buzzword is WNRO - Week Number Roll Over.
  https://en.wikipedia.org/wiki/GPS_Week_Number_Rollover

There is a 10 bit field for the week number in the GPS data format.  That's 
about 20 years.  GPS has been running for over 40 years now.  It's rolled over 
twice.

You can fix it in software by adding 1024*7 days until you get something that 
is reasonable.  One simple test for reasonable is the date/time the software 
package was compiled.

Some GPS units allow you to give them a starting date/time.  I don't know if 
the TBolt does that.  The HP Z3801A does.



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