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Also checked against www.time.gov, which claimed accuracy with 4.5
seconds, and it matched the computer, not the cell phone.

AT&T uses GSM.  I'll check on the wife's phone, which is a different
brand but still AT&T.

On Apr 22, 2008, at 6:26 PM, Fred Hebard wrote:

> On a mac, using time.apple.com.  Just synced, and still about 50
> seconds slow.
>
> On Apr 22, 2008, at 6:12 PM, Lu Abel wrote:
>
>>
>> Fred:
>>
>> I'm not an expert on cell phone technologies, but it may be that
>> AT&T is
>> the one provider that may not need accurate timekeeping to make its
>> particular technology work.
>>
>> When you say you're on a network time server, are you on a
>> Windows, Mac
>> or Unix machine?   Windows only resynchronizes the computer's
>> time-of-day clock with an NTP server once a week (or even less
>> frequently);  I've seen at least one of my computers drift
>> considerably
>> in between.   I just checked my new Vista PC computer's clock against
>> time.gov, it's three seconds slow with a resynchronization
>> scheduled for
>> Friday.   But it could just as easily be fast, as yours might be.   I
>> personally have a lot of faith in time.gov (especially with a
>> broadband
>> connection) because it attempts to measure and compensate for any
>> network delay.
>>
>> Wait, I forgot that I also have one of those digital clocks that
>> synchronizes itself to the low-frequency time signal broadcast by
>> WWVB.
>> It appears to be between 0.3 and 0.5 seconds slow as compared to the
>> www.time.gov display on my computer.   On the other hand, considering
>> that it cost me all of $6, I have to wonder whether its time
>> display is
>> more or less accurate.
>>
>> Lu
>>
>> Fred Hebard wrote:
>>> I followed up on this when it was mentioned previously on this list,
>>> and I believe the accuracy of cell phones may vary with the network.
>>> I'm on AT&T, and my impression is that the time is not accurate.
>>> For
>>> instance, my phone now says it's 9:51:55 and my computer says it's
>>> 12:52:42.  The computer is getting its time from a network time
>>> server.  These may be more accurate than the USNO site, but, I don't
>>> know this one way or another.
>>>
>>> Fred Hebard
>>>
>>> On Apr 22, 2008, at 11:56 AM, Lu Abel wrote:
>>>
>>>
>>>> Bill:
>>>>
>>>> The time difference between your Garmin and the USNO web site is
>>>> likely
>>>> due to network delays (ie, the USNO sends you a time pulse at the
>>>> correct time, but it takes almost a second to arrive at your
>>>> computer).   The other web site run by USNO, www.time.gov, says it
>>>> attempts to measure network delays and compensate for them.
>>>> Another
>>>> source for accurate time is your cell phone.  Mine only keeps
>>>> time to
>>>> the minute, but it very accurately rolls over at the 60-second
>>>> mark.
>>>>
>>>> Lu Abel
>>>>
>>>> Bill wrote:
>>>>
>>>>> The current discussion on time, relativity and leap seconds is, in
>>>>> many
>>>>> areas, well above my head.  Noting the various flavors of UT
>>>>> (currently), an
>>>>> observation and a pragmatic question for cel nav.
>>>>>
>>>>> The seconds readout between my GPS (Garmin GPS 76) and
>>>>> http://tycho.usno.navy.mil/cgi-bin/anim
>>>>> differ by about one (1) second.
>>>>>
>>>>> The web site (dial up modem at the moment) is nominally one (1)
>>>>> second
>>>>> behind the GPS readout.
>>>>>
>>>>> Bringing it into the realm of traditional navigation, which time
>>>>> do I use to
>>>>> set my hack watch? ;-)  Potentially a quarter mile intercept
>>>>> difference
>>>>> under ideal circumstances.
>>>>>
>>>>> I do not have access to a time-signal radio now.
>>>>>
>>>>> Bill
>>>>>
>>>>>
>>>>>
>>>
>>>
>>>
>>>>
>>>
>>
>> >>
>



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