[time-nuts] Trimble Thunderbolt no longer determines thecorrect date

[Mark Sims]

That is basically what Lady Heather does.  Heather converts all date/time values to JD and works internally with those.  If a rollover is detected, 1024 weeks worth of seconds is added.  This has worked for all the receivers I have that have rollover problems.   

One of my Motorola receivers went into rollover a few months ago and Heather caught the moment.  The previous day the date/time was OK.  The next day it was showing rollover and I assumed it was due to a power glitch,  but the date shown was correct (and not a false rollover with the year 2037 showing... which can happen if the receiver resets, loses the almanac, sends 20 minutes of bogus dates, then re-acquires the almanac).  Indeed the receiver had passed its freshness date.

Once Heather detects a rollover condition, the rollover correction latches on.  It does not reset if the receiver starts sending valid dates.  It does this so you have a warning that something went awry with the date/time messages.

If you are doing a Tbolt monitor, I would not recommend blindly adding 1024 weeks to the date/time.  Check the year first.  There may be firmware out there with different rollover dates.  Also, do some filtering on the receiver date/time.   I have seen some cases where the Tbolt or other Trimble receivers momentarily send bogus date/time values or send a corrupted packet.

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> Sample code to add 1024 weeks is at www.leapsecond.com/tools/tbolt1.c if that's all it takes to patch the date field in the packet