[ntp:questions] Start of new GPS 1024 week epoch

Rob nomail at example.com
Thu Aug 15 07:34:24 UTC 2013

David Taylor <david-taylor at blueyonder.co.uk.invalid> wrote:
> On 14/08/2013 17:44, Rob wrote:
> []
>> How does a "good" receiver know the correct time?  Does it rely on
>> local (backed-up) storage, or is there some way of receiving it via
>> the almanac?  Or are "good" receivers hardwired as well, only with
>> a different valid span?
>> I would not be surprised when "good" receivers turn out to have just
>> a different moment or mode of failure.
> []
> Some receivers have battery backup, in fact all but one of the receiver 
> types I use have this.

Ok but what happens when the battery is replaced?

> I have an awful feeling that you are right about the potential for 
> failure - it might take 19 years to find out, though!

Well, the first rollover was in 1999 and the next one will be in 2018.

Warnings went out about the problem in 1993, and manufacturers started
to implement fixes for it.  It can be expected that the first problems
arising from those fixes will appear 19 years later, i.e. in 2012.
Manufacturers that were implementing their fix after one year have
their problem now.   Manufacturers that waited 2 years have it next
year.   We might have problems all the way up to 2018.

Of course those manufacturers that updated their fix every time they
released new software, automatically or not, (like what is apparently
done in ntpd) can get by whenever the life of their products is less
than 19 years after the last software update.

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