I have a character who ends up jumping backwards in time by 24 hours. Essentially nothing else changes, but the character has their jPhone in their pocket at the time of the jump. How functional should I expect this piece of modern tech to be after the time warp?

I assume that many applications will be perfectly functional- the phone's compass, for example, or the flashlight. Apps like phone calls or internet access are more questionable, given that there's a whole digital world there that relies on specific protocols for its continued function. Is this a realistic assessment? Or did he just brick his $999 jPhone?

This question graduated from the Sandbox!

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    $\begingroup$ You can test this for yourself. Turn off automatic time updates and set the clock on your phone forward by 24 hours, then turn automatic time updates back on. $\endgroup$
    – Mike Scott
    Jan 5, 2018 at 6:02
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    $\begingroup$ The only small problem is be that there be two phones with the same IMEI and SIM on the cellular network. The network won't like it. $\endgroup$
    – AlexP
    Jan 5, 2018 at 10:25
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    $\begingroup$ @Mołot No it's not. This is about what happens to a phone after going through a time warp. That's an element of the OP's world. Worldbuilding pure and simple and on topic. $\endgroup$
    – a4android
    Jan 5, 2018 at 11:28
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    $\begingroup$ @Mołot On the other hand, the question suddenly becomes valid if you ask "What problems would a secret community of time travelers have to overcome in regards to technology?" $\endgroup$
    – Muuski
    Jan 5, 2018 at 14:24
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    $\begingroup$ I don't think that the downvotes are really appropriate. What other stack exchange site would take this seriously? it would be more off topic elsewhere. This is a simple question that seems fairly useful for any stories dealing with time travel and technology. It's not a fantasy or futuristic science fiction question, but it's still 100% relating to world building. $\endgroup$
    – Jonathan
    Jan 6, 2018 at 14:26

4 Answers 4


This should be a relatively simple issue. Events like it happen all the time when a computer gets a wrong clock setting from somewhere.

As soon as the phone connects back to the internet, it'll connect to an NTP server and get the new "correct" time. End-user devices (like phones, laptops, tablets, etc) are almost always configured to assume that if their clock is wrong then they have messed up somehow, and as such will assume that an upstream server is more correct.

So, in your case, the jPhone will report the time as the time that the traveler left (24hrs ahead), until it connects to the internet. Once it does, it will contact an upstream server, assume it's clock is incorrect, and change its clock to reflect the current time that the traveler has jumped to (24hrs back).

This is all assuming that the phone wasn't in the middle of an update at the time. If so, then it could get dicey.


Truth be told it's unlikely you'd see any effect at all. Most networking functionality is designed to work with as little information as possible and such a discrepancy would be well within tolerances for normal errors.

Soon after traveling back in time your phone would check in with a time server and realise 'oops I'm a whole day ahead' and correct itself to the current time, and from there everything would pretty much work as normal.

You might cause a bothersome race condition for the phone company trying to route calls to you for 24 hours but it's easily solved by getting another sim until your phone is unique again. If you're on the same physical network as your past phone the router probably won't route to your phone properly until you move away due to a mac address conflict.

Unfortunately this isn't a terribly exciting answer - since all network protocols can be spoofed by someone with a computer and a network interface, everything pretty much doesn't blink when it comes to a couple of phones with the same info.


Your phone should be perfectly fine. It would be similar to setting your phone to manual sync and then setting it back a day.

The digital apps might have some extra downloading to do. Any app that is online or requires you to be synced up will most likely wipe the data off your phone and re-sync the data, but this really depends on the app. Other apps, like camera for example, would still have the photos. This wouldn't corrupt them and you would just get new photos with a weird name like 20171010(1) if they have matching names.

If your phone is on auto sync, your time would instantly jump back and any games that rely on time (not online synced) would just revert back. If you were in an update, chances are it would either abort (if you haven't finished downloading) or finish as normal (you have all the files downloaded, the install will finish).

This is of course, assuming the time warp doesn't physically alter anything on your phone.


Phone, per se, no. It will take the network date as accurate and figure it's wrong. If you're running any time-limited trial versions they might not like it, otherwise all you risk is wrong-way-sync errors, yesterday's data overwriting today's.

However, you have a paradox problem. You have two identical SIMs on the network and they will conflict. You at Jump-23 will be conflicting with you at Jump+1. The call you received at Jump-23 might end up going to Jump+1 instead--and you just changed your own past.

It's conceivable that the network might call shenanigans on the duplicated SIM, also, and shut down your account. An even bigger paradox problem if it happens.


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