[tz] Utah may drop DST

Patrice Scattolin patrice.scattolin at oracle.com
Thu Oct 16 12:41:21 UTC 2014

The fundamental reason this doesn't work is that TZ info needs to be 
know about AHEAD of time so that scheduling tasks (plane tickets, 
scheduled meetings in the future across timezones (EDT to PDT for 
example)) can be scheduled correctly before the change in TZ occurs. 
(and that explains why short lead time before a change in TZ rules is a 
bad idea)

Unless you have devices with built-in time machines to go probe cell 
towers time signal in the future, this doesn't solve the problem.

What you suggest though could be useful to set watches or microwaves to 
the correct local time using OTA data like the clocks that derive their 
time from atomic clock radio signals. To my knowledge that signal 
doesn't include any TZ info. Seeing the low value in these devices I 
doubt there will be pressure to pay for the infrastructure for such a 

Beside, as far as I know, cell many compagnies are on this list and have 
contributed to the data here so they pretty much find out when we do.

On 16/10/2014 4:58 AM, Zoidsoft wrote:
> I was thinking of the Seti at home app that used to be popular back in 
> the 90's.  Before that I always had to set the time on all my 
> devices.  In my experience my cell phone has updated time change info 
> on something other than the tz database.  I don't know how Verizon did 
> it (unless it's through complex shape files), but when driving by 
> Vidal, it was on Arizona time; 6 miles north it switched to Pacific 
> time.  I know because I let the tz database know about this strange 
> little town which Verizon somehow knew about and kept time with 
> (probably only a population of about 12).
> Perhaps an iterative process like this could help improve accuracy 
> when users change the time standard when it is wrong sending that info 
> back to a server that the tz database reads?
> On Thu, Oct 16, 2014 at 4:25 AM, Jonathan M Davis <jmdavisProg at gmx.com 
> <mailto:jmdavisProg at gmx.com>> wrote:
>     On Thursday, October 16, 2014 03:49:56 Zoidsoft wrote:
>     > This might seem like a stupid question, but now that most of the
>     world is
>     > connected by computers, smart phones, etc... why don't we
>     develop an app
>     > that collects time settings and standards along with GPS for
>     every device
>     > world wide as to what is showing on the clock?  Such an app
>     could then
>     > automatically generate zone rules along with location data for
>     each of
>     > those rules.  It would be a complex exercise in set theory
>     getting the
>     > program to recognize "groups" of similar data but I think it
>     could be done.
>     The first question that comes to mind is how on earth each of
>     those computers
>     would get the time in the first place. Its the TZ database that
>     this list is
>     for that's used to give most of them the information that they
>     need to give
>     the time in a local time zone rather than UTC. All that stuff like
>     NTP does is
>     give the current time in UTC, so without something like the TZ
>     database, all
>     any of those devices would know about would be UTC.
>     Also, time zone rules change over time, and we often need to know
>     what they
>     are ahead of time, so trying to figure out what they are via AI
>     would not only
>     be a mess, but it wouldn't even have the information that we need
>     when we need
>     it. If all you cared about was generating a database of what a
>     bunch of
>     devices _thought_ that the time was in a given time zone at
>     different points
>     in time was, that would be one thing, but we care about having the
>     correct
>     rules over pretty much as large a time span as possible - both in
>     the future
>     and in the past. And what you're suggesting wouldn't work for that
>     at all. AI
>     can be great for heuristics, but it's horrible if you need to know
>     the exact
>     anwser to something - like what the time zone rules are _exactly_
>     for a given
>     time zone at any given point in time.
>     But really, what you're suggesting pretty much comes down to
>     generating
>     information from a group of devices instead of looking it up in
>     exactly the
>     same place that they look it up, because the only way that they
>     know anything
>     about the local time zone that they're in is because of the TZ
>     database. They
>     don't magically learn it just because a government announces it.
>     They learn it
>     because their TZ database files get updated with it.
>     - Jonathan M Davis


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