[time-nuts] GPS week rollover

[Pete Stephenson]

On Wed, May 6, 2015 at 6:48 AM, Mark Sims <holrum at hotmail.com> wrote:
> Well,  a big one will be in 2017 when all our Tbolts roll over.    I have included some code in the next version of Lady Heather to compensate.  If it detects a year from the unit before 2015,  it converts the date/time to Julian,  adds 1024 weeks worth of seconds,  and then converts the date/time back to Gregorian.  You can also specify a user defined rollover adjustment (in seconds).  One issue that I have seen is the Tbolt occasionally spitting out a bogo-year and triggering a false/premature rollover...  still trying to track that down.
>
> People using Tbolts for things like NTP servers will have to implement a similar fix...

I assume the Tbolt rollover will be problematic for those who start
their Tbolt completely cold (no time, almanac, or ephemeris) and
without any non-GPS input, but how will the Tbolt behave in situations
where the user initializes the Tbolt with the then-correct
post-rollover date and time? For example, one might use Tboltmon and a
wristwatch to set the approximate time on the unit and then let it
figure out the precise time from GPS.

Also, will the rollover cause time-of-day problems for running Tbolts?
That is, would they "ride through" the rollover and continue to
provide the correct date and time as expected (that is, they recognize
that a rollover occurred and keep working normally so long as they're
not cold-reset) or would they immediately jump back to December 14,
1997 (the Thunderbolt "zero" date)? According to
<https://www.febo.com/pipermail/time-nuts/2014-September/086664.html>
it looks like they'll output the incorrect date as they cross over the
rollover point. That's not good.

-- 
Pete Stephenson