[ntp:questions] Can or should the NTP protocol eventually serve timezone data?

Matt Nordhoff mnordhoff at mattnordhoff.com
Thu Jun 18 12:51:55 UTC 2009


Richard B. Gilbert wrote:
> Unruh wrote:
>> "Richard B. Gilbert" <rgilbert88 at comcast.net> writes:
>>
>>> Rob wrote:
>>>> Richard B. Gilbert <rgilbert88 at comcast.net> wrote:
>>>>> Rob wrote:
>>>>>> Richard B. Gilbert <rgilbert88 at comcast.net> wrote:
>>>>>>> I believe that the O/S vendors supply a file with timezone data.  If you 
>>>>>>> have support, you can even get updates from the vendor.  Since I can't 
>>>>>>> afford support (I'm retired and a hobbyist) I have to do it by hand.
>>>>>> As Jan Ceuleers also pointed out, the problem is not at all limited
>>>>>> to operating systems.  Any device that obtains time using NTP and wants
>>>>>> to display it in local time needs the info.
>>>>>> This could just as well be a digital clock.
>>>>> I have a couple of "radio controlled" digital clocks and a wrist watch 
>>>>> that do it automagically.  The VLF broadcast from WWVB provides the 
>>>>> necessary info.
>>>> That cannot be true.  It may work for your location, but I'm sure it
>>>> does not cover the general case under discussion.
>>> How can it not be true?  The time broadcast encodes both the time 
>>> (standard time) and whether or not DST is in effect.  Of course it 
>>> doesn't work for those jurisdictions that have chosen to go there own 
>>> way as far as DST is concerned.
>> But there are at least 10 different timezone/DST rules for the USA. How does WWV broadcast
>> them all?
> 
> Sorry, but I believe that only four time zones are sufficient to cover 
> the continental U.S.  If you include Alaska and Hawaii you need two 
> more.  Where did the other four come from?  Of course any jurisdiction 
> CAN make its own rules for DST but most do not.

Lots of weird things have happened over time. Skimming zoneinfo's
northamerica file, one example is that Eastern Crawford County, Indiana
didn't observe DST for decades. Michigan didn't observe DST for a few
years back around 1970, and did it differently in 1975. Most of this is
historical, of course, but Arizona still doesn't observe DST (except for
the Navajo Nation).
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