<div dir="ltr">the NITZ string doesn't include an olson id. if you look at GsmServiceStateTracker.java or the CDMA equivalent, you can see the heuristics for turning a gmt offset, country code, and "is_dst" flag into an olson id. (actually, every part of the NITZ string is optional.)<div>
<br></div><div>cell towers can be misconfigured, which adds to the fun. plus there are places like the canary islands that don't have an MCC and don't share a time zone with the country that they share an MCC with.</div>
<div class="gmail_extra"><br><br><div class="gmail_quote">On Tue, Sep 24, 2013 at 9:42 AM, Dennis Ferguson <span dir="ltr"><<a href="mailto:dennis.c.ferguson@gmail.com" target="_blank">dennis.c.ferguson@gmail.com</a>></span> wrote:<br>
<blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex"><div class="im"><br>
On 23 Sep, 2013, at 16:32 , L. David Baron <<a href="mailto:dbaron@dbaron.org">dbaron@dbaron.org</a>> wrote:<br>
<br>
> On Monday 2013-09-23 13:07 -0700, Paul Eggert wrote:<br>
>><br>
</div><div class="im">>> end users in Israel. Many cellphones running Android,<br>
>> BlackBerry, iOS, and Symbian were still based on tz release<br>
<br>
</div>My previous phone was a Symbian phone. I wouldn't update it<br>
since that generally made it worse than it already was...<br>
<div class="im"><br>
> It also seems odd that these phones didn't have their time adjusted<br>
> as a result of receiving NITZ messages from cell towers with the<br>
> correct UTC offset. I thought that using time and timezone<br>
> information from the cell network was the typical default<br>
> configuration on smartphones (which makes having an up-to-date<br>
> timezone database less critical).<br>
><br>
> Are there carriers in Israel that don't broadcast date and offset<br>
> information from their cell towers? Or were the carriers<br>
> broadcasting incorrect data?<br>
<br>
</div>GSM towers traditionally had no idea what time or timezone it is,<br>
and many (maybe most) GSM and UMTS base stations still don't. NITZ<br>
isn't very common. I think the "TZ" part of NITZ may have been<br>
invented to solve a problem specific to American carriers, that<br>
they were deploying GSM into a market where the competing digital<br>
technologies (CDMA and IS-136 TDMA) could set the time and timezone<br>
on the handset and didn't want their GSM service to not have that<br>
feature too. I've seen the "NI" part of NITZ, without the TZ part, in<br>
use in China (despite what the Wikipedia page says) to identify the<br>
"area" the tower you were connected to was in, since they used to<br>
charge people different prices for calls in and out of their "home"<br>
area. In any case, outside of the Americas it is fairly rare to<br>
find a carrier which provides this service, so smartphones seem to<br>
often include plain old NTP and time zone files as a fall back while<br>
dumb phones need their clocks set by hand.<br>
<br>
Note that in the US mobile phone base stations always know what<br>
time it is since they pretty much always have GPS receivers, for<br>
E911 positioning if not for network time synchronization. In<br>
many other countries, however, it is considered a bad idea to<br>
allow your telecommunications infrastructure to become dependent<br>
on a service owned and operated by a foreign military so they<br>
are less likely to do this.<br>
<span class="HOEnZb"><font color="#888888"><br>
Dennis Ferguson<br>
</font></span></blockquote></div><br><br clear="all"><div><br></div>
</div></div>