[time-nuts] Handy iPhone app

Peter Monta pmonta at gmail.com
Fri Jul 16 05:00:22 UTC 2010


Oz-in-DFW writes:

> > ... There is no way AT&T would be 12.4 seconds off ...
> >
>
> I used to work in the cell infra business.  While it's less true today,
> there are still a number of operators that do not sync system clocks.
> The time supplied to users can be **minutes** off.
>
> Most newer operational standards can't tolerate this and "accurate" time
> (better than a ms) is important.  WiMAX requires TDD base stations to
> base station alignment to be better than 1 microsecond.  Most telecom
> operators want to avoid GPS at every site. It's a logistical PITA.

Here in the Bay Area, AT&T/iPhone time has gotten noticeably worse
recently.  The error used to be around 4 seconds; now it's 49 seconds (!).

Emerald Time is fine for interactive use, but what I find very impolite
is that AT&T's bad timestamps are written into the EXIF headers on photos.
Sometimes I take pictures of sundials, for example, and a 49-second
error is not negligible for a carefully made dial.

It would be amusing to arrange for a long-term record of the offset of
one's phone (which can of course change across multiple providers during
travel), say by using a background process to take a sample every few hours
against NTP sources or against GPS if the phone has it (or both).
Then any photos can be batch-corrected later if desired.  Apple, give
me control over the time on my own phone, and please don't force me to
resort to these schemes :-).

Cheers,
Peter Monta



More information about the time-nuts mailing list