
Did iOS 9 set millions of iPhone clocks to the wrong time? - jameswilsterman
http://www.volleythat.com/essays/2015/9/22/did-apple-just-set-millions-of-iphone-clocks-to-the-wrong-time
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PhantomGremlin
I monitor ntp activity from the computers and iPhones on my home network, so I
have a good understanding of how Apple does this, at least on OS X and iOS
8.4, at least when WiFi is available.

It's simple ntp. The computers ask DNS for time.apple.com, while the iOS
devices ask for a similar domain, time-ios.apple.com. From that point both
types of devices make ntp requests. What I do on my firewall is redirect those
requests to my local ntp server, this saves on external ntp traffic.

time.apple.com resolves to 12 different IP addresses, all on Apple's
17.0.0.0/8 network. It's easy to see, just issue the following command and
you'll see all of them:

    
    
       ntpdate -quv time.apple.com
    

These servers are pretty darn good, they're stratum 1, they're distributed all
over the world. Time from them seems to agree to within milliseconds of each
other. The iOS address only seems to resolve to 3 places, but those also agree
to milliseconds of each other.

Given that, I can think of at least 3 different error scenarios:

1) Apple broke something in actual ntp implementation in iOS 9.

2) One of the iOS ntp servers is goofing up. Unlikely since I'm sure Apple
doubtlessly has lots of monitoring for errors like that.

3) Without WiFi available, iOS relies on the cell carrier for time services.
Of course, the operation of the cell network depends on all phones knowing the
exact time, but that probably doesn't carry over to something ancillary like
ntp. Perhaps a carrier's ntp server is borked?

To resolve this it would be interesting to know and try:

    
    
       does the problem happen only on WiFi?
    
       does the problem happen only on cellular?
    
       does the problem only happen with a specific carrier?
    
       if WiFi, use something like tcpdump to monitor the
       actual packets to see if any obviously bad time is
       being served
    

Why would anyone update to 9.0.0 anyway? New software always has teething
problems.

~~~
toufka
It affects (non-cellular) iPads with iOS9 as well, so likely not a carrier-
related issue. So it's not issue #3. And like you say, a lot more than iOS9
would be out of sync if it was #2. So we're going to have to go with #1 -
Apple broke something in ntp.

~~~
waz0wski
wonder if it's due to something that's changed as part of the battery life
improvements, from process scheduling to clockspeed changes

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mrks_
Easier way to check if your phone is affected:
[http://time.is](http://time.is)

My iPhone running iOS 9 (updated launch day) is 17 seconds ahead!

~~~
cimbal
New iPad (iOS 9.1) was 3.6 seconds ahead. I disabled automatic
synchronization, set the clock manually and then turned synchronization back
on. Everything looks fine now, with only +/\- 0.044 seconds error.

Too bad i don't know if turning it off and on again would have worked too.

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sigmar
Any idea why the time is incorrect? Does forcing a synchronization of the
clock in the settings fix it? (Don't have an iphone, so I'm unsure if such an
option exists)

~~~
mlchild
Not sure why it's incorrect, and turning on/off the automatic synchronization
in Settings doesn't seem to do anything.

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joezydeco
I have a little desktop clock that synchronizes to WWV every night. My
iphone5S is about 6 seconds fast.

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raspasov
Mine is 5.5 seconds ahead!

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mookie
Mine is 35 seconds fast! iPhone 6 on verizon

