What Time is it? Your iPad 2 *Still* Doesn’t Know

| How-To

Previously, I looked at the iPad 1 (Wi-Fi only) internal clock and found that it is left to drift on its own. Without aid from a cell tower clock, like the GSM models, or periodic sync to a Mac, the iPad 1 clock has no way to set itself to a time standard. Worse, apps are forbidden by Apple to reset the internal clock. Testing of an iPad 2 shows that its clock is no better in this regard.

Back in February, 2011, I found that a Wi-Fi only iPad 1 was not invoking an NTP daemon to check with an external time standard over that Wi-Fi connection. Apple seems to have determined that this is not necessary, even though, without constant calibration, the iPad 1 clock can drift by a second per day, sometimes much more. In addition, it was found that with iOS 4.2.1, clock syncing does not occur when connected to a Mac via iTunes.

The upshot is that doctors, astronomers, private pilots, researchers and others who depend on the clock in the Wi-Fi only iPad could find themselves many minutes off from the actual time, and that’s unacceptable for many purposes.

iPad 2 Update

My testing of a Wi-Fi only iPad 2 has shown that the situation is no better. With iOS 4.3.2, I found that syncing of the time still does not occur when connected to a Mac via iTunes and a full sync + backup is applied.

In addition, the oscillator that Apple has chosen for the iPad 2 doesn’t seem to be any better than that in the iPad 1. Over the past few weeks, I have been keeping a log of the time offset between an NTP time standard and the iPad 2’s internal clock. I did this by running an app from Emerald Sequoia called Emerald Time. It shows the offset, and then I would snap an iPad 2 screen shot to provide a photographic log — like this:

Emerald Time

The iPad 2 offset (fast in this case) is shown in red: -20.549 sec.

I read the data off the screen shots and entered it into Apple’s Numbers spreadsheet, then created a chart. The data points have a linear, least squares fit applied. Here’s the chart of the drift.

iPad 2 clock drift

Negative values in the chart indicate that the iPad’s internal clock is behind, positive numbers indicate that the iPad’s clock is running ahead of official time. This trend, from behind to ahead, is repeated on the iPad 2 from the iPad 1, that is, both clocks on my iPads run slightly fast. In the data above, the iPad 2 clock is gaining about 1.67 seconds/day which is almost a minute a month. (I switched the sign of the offsets to make the chart easier to read.)

Conclusion

Apple uses an oscillator in my iPad 2 that drifts just as much as the one in my iPad 1. The measured drift, in the iPad 2, is about 1.67 seconds/day. Nothing has changed in the iOS so that this Wi-Fi only iPad is time synced to a Mac when connected and synced. That would help a lot because Macs are typically connected to a time standard (by default time.apple.com) via NTP.

For users who must have good accuracy with their Wi-Fi only iPad 1 or 2, I strongly recommend Emerald Time, linked to above, and weekly resets of the iPad’s internal clock.

Comments

Ken

Agreed, but in conclusion you suggest “weekly resets of the iPad?s internal clock.” Good idea, but how does one go about resetting the internal clock on both iPhone and iPad?

Deb

I thought I had read that Emerald Time *was* updating the clock when you run it.  I’ve no way to prove that, tho…..

John Martellaro

To set the iPad or iPhone clock:

Settings -> General -> Date & Time -> Set Date & Time

1. Change the minute value on the dial by a minute or two.
2. Set it back to the correct minute you want, coming up, as determined by a standard, like your Mac clock. Watch the time standard until the next minute comes up.
3. On the exact minute, close the settings window by tapping outside it.

You should be within a second at that point.  It may require some practice.

John Martellaro

Deb: The co-author of Emerald Time told me that Apple forbids developers from changing/adjusting the internal clock.

Noah

Maybe I’m lacking in imagination but what application could possibly be so important that seconds count and yet rely exclusively on an iPad for timing?

other side

You should be within a second at that point.  It may require some practice.

A Windows-esque fix for a problem that shouldn’t exist.

Apple, the clock in my old Chevy is more accurate than this.  Perhaps you should contact GM for advice on how to implement a clock (and yes I’m being snide here).

And speaking of autos, I’m starting to see shades of Toyota here: too big too fast, and losing quality in a rush to be #1.

other side

Maybe I?m lacking in imagination but what application could possibly be so important that seconds count and yet rely exclusively on an iPad for timing?

The problem is such severe time creep, in a state-of-the-art product, from a company allegedly known for high polish & obsessive attention to detail.

It should be just slightly embarrassing when a dime store watch keeps better time than an $800 device.

geoduck

FWIW my iPod Touch seems to do the same thing.
This is silly. 15 years ago i had my computers set up to check an internet time standard. Even Win95 machines would do this. They don’t have to do it often. How about once a day or the next time you connect to the Internet. Poof Problem solved.

Maybe I?m lacking in imagination but what application could possibly be so important that seconds count and yet rely exclusively on an iPad for timing?

Seconds might be a bit much but they build up. roughly 30 seconds every 15 days=a minute a month, don’t reset it for a year and you’ll start being late for iCal appointments. Don’t know about these systems but I know the servers I support start acting weird if they are off by a few minutes, apps stop working, systems won’t update, logins fail. While seconds might be closer than most people need, within a minute at all times is not unreasonable.

And speaking of autos, I?m starting to see shades of Toyota here: too big too fast, and losing quality in a rush to be #1.

You might be on to something here. Like the log of where you’ve been everyone’s been talking about for the last few days. Why didn’t they have a automatic purge coded in? Or give the user the option to delete it? I suspect the forgot about it.

webjprgm

Out of curiosity, how does the Blizzard extra account login security app work, the one that generates random numbers in an iPhone app that Blizzard servers can also generate so you have a code that changes every ~15 sec?  Does that need an accurate time?

Here’s what my Googling found:
http://wow.joystiq.com/2009/03/19/authenticator-app-coming-to-iphones-ipods-and-other-mobile-dev/

It just says you need wi-fi / cell tower access to set up the Authenticator first.  It makes no mention of whether this depends on the system clock, but it certainly is not checking a network clock each time.

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