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How accurate is your cell phone?

by Jordan Ficklin

This is a plea for help in conducting an experiment for the horological community. Many people compare the accuracy of their fine timepiece to the time on their cell phone. They, as have I, assume that this signal which is received from cell towers is accurate but it may not be so. I would like to compile some data as to the accuracy of these devices to help out the general horological community. Will you help me out?

Here is what you need to do:
For the next 5 days check the time of your cell phone compared to the time at
Download the excel spreadsheet here (right click and choose save as)
Fill in the values in the spreadsheet and email it to me at the end of 5 days.

The very adventurous could check their phone multiple times a day in multiple locations and report the results. (Feel free to modify the spreadsheet as needed)

Below is an image of the Excel Spreadsheet. Fill in the phone Make, Model, and Network Info. Visit and compare the time on your phone with the time at the web page (sample image below) (circled in red). Fill in the error given (circled in blue). At the end of 5 days email me the spreadsheet. I’ll fill it all in and let the community at large know how accurate our cell phones tend to be.

Note: If your phone doesn’t show the seconds be sure to wait until the minute clicks over and record the time at the changeover.


P.S. Comments from those of you with first hand experience in the world of cell phones on accuracy would also be greatly appreciated.

Thank you.

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  1. J.Peter
    Posted July 23, 2012 at 8:40 pm | Permalink

    I’ve already heard some interesting anecdotes about phones being off by quite a bit of time. But what is really important is the precision, not the accuracy. I want to know if the amount they are off changes or if they tell time consistently.

  2. Magnus Falk
    Posted July 24, 2012 at 1:26 am | Permalink

    In order for this to be any good the phone needs to actually be set to receive time updates from the cellphone tower, the cellphone make and model shouldn’t really matter. Though I don’t think I’ve heard of any nodes not running NTP, that should really be an exception.

    /Working at Ericsson, testing LTE (4G) nodes

  3. Posted August 21, 2012 at 1:20 pm | Permalink

    About a week ago out of the blue I noticed that my phone (Verizon) was saying it was about 40 hours into the future. I tried resets and re-acquiring… But it was like that for several hours, then suddenly it corrected itself. Something like that is enough to cause havoc. I’m sure it doesn’t happen very often.

  4. Cirrus
    Posted August 28, 2012 at 4:02 am | Permalink

    My mobile takes its time from the network (3), but the network time isn’t consistent! Today my mobile is +5s compared to the UK Atomic Clock, but yesterday it was +35s… my 40 year old automatic SeaStar is more reliable, and that just doesn’t seem right ­čśë

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