There's support in "over the air" ATSC digital TV signals for DST info,
but most TV stations aren't known  for keeping their time information up
to date.  There's a system time packet that has the GPS time, the number
of seconds difference between GPS time and UTC (and a lot of stations
don't get that right either), and then a day and hour indicator saying
when a DST to standard time (or vice versa) is supposed to happen.  That
indication is supposed to be present soon after it is unambiguous, i.e.
the transition is less than 28 days away. But I believe it is up to the
local station to program most of that, and some stations get it really
wrong.

Regardless, you are trusting someone to configure DST information
somewhere. Obviously it's easier to trust the folks at NIST to get it
right, rather than your local TV station. If you go with static DST
configuration rules then  you have to trust yourself to update the
information as appropriate.

Someone suggested scraping the NIST time service website for this
information.  The NIST website specifically says "Also, it is
inappropriate to generate your own software to use the functionality of
this site. Contact us for details."
It might be interesting to send an email to timeinfo@boulder.nist.gov
and ask them what they would suggest for getting accurate DST
information, but I doubt they will suggest anything that hasn't already
been proposed.

Regards,

John

 8/24/2018 11:18 AM, Mark Sims wrote:

Good Idea, John.
I'll do that.
Just to see what they say.

--- Graham

==

On Fri, Aug 24, 2018 at 1:25 PM John Marvin jm-tnut@themarvins.org wrote:

Hi

Yet another reason to avoid closed source / packaged solutions ……

Bob

Is there more of it?  What I see makes no reference to WWVB.

Dana

On Fri, Aug 24, 2018 at 1:10 PM Graham / KE9H ke9h.graham@gmail.com wrote:

There seem to be 2 :
https://petitions.whitehouse.gov/petition/proposed-shutdown-nists-wwv-and-wwvh-radio-stations

On Fri, Aug 24, 2018 at 8:44 PM, Dana Whitlow k8yumdoober@gmail.com wrote:

On Fri, Aug 24, 2018 at 1:25 PM John Marvin jm-tnut@themarvins.org wrote:

RBDS/RDS (transmitted by FM broadcast stations) includes UTC and a
local offset (1/2 hour intervals from -12 to +12 hours -- sorry
Kiribati, Tokelau, Samoa, et al).  But, in North America, like TV
stations, FM stations are lucky if they have a part-time contract
engineer who knows how to set up the parameters in the first place let
alone make sure they stay set.  No specific DST field I can see but
presumably the station's RDS software package can manipulate the local
offset twice a year.

I'm a little surprised at the number of people on this list, of all
places, that are incensed that the government won't set their clocks
for them twice a year (assuming the administration's budget proposal
is approved by Congress).  I don't muck with non-NTP capable stuff so
in my world, timezones and summer time are local display aberrations
that aren't the responsibility of whichever protocol is giving you the
tick (nor should they be IMO).

I might also note that the US Congress has only mucked about with
summer time twice since 1986.  Thank goodness.

Did I see someone mention actually scraping NIST's webpages for time?
Why on earth would anyone do that when NTP clients have been widely
available for decades at this point?

--
Peter Laws | N5UWY | plaws plaws net | Travel by Train!

Unfortunately, this one is inaccurate.  It talks of impact to radio
controlled "Atomic Clocks", but does not mention WWVB, only WWV and WWVH.

David N1HAC

On 8/24/18 3:51 PM, Adrian Godwin wrote: