Get Real Time - Not Device Set Time in android

Question

How to find out the Real Geographical Time, as in my application I want to attach the real time with my application.

So that if the user changes the time in his device then I should get only the real prevailing time - NOT THE DEVICE TIME

My question is much confusing but try to understand in a simple language -

I dont want DEVICE TIME, I want REAL PREVAILING TIME at any instant

Solution 1

You need to use the NTP (Network Time Protocol) protocol:

Here is some code I found somewhere else... and I am using it. This uses the Apache Commons library, which can be installed using Gradle (adding a dependency on commons-net:commons-net:3.6)

If you need a list of time servers, check: http://tf.nist.gov/service/time-servers.html

Here is some Java Code for you to use:

public class TimeLookup {
    public static final String TIME_SERVER = "time-a.nist.gov";

    public static void main(String[] args) throws Exception {
        NTPUDPClient timeClient = new NTPUDPClient();
        InetAddress inetAddress = InetAddress.getByName(TIME_SERVER);
        TimeInfo timeInfo = timeClient.getTime(inetAddress);
        long returnTime = timeInfo.getReturnTime();
        Date time = new Date(returnTime);
        System.out.println("Time from " + TIME_SERVER + ": " + time);
    }

}

Note the Android code must run on the background thread and include gradle dependency:

implementation 'commons-net:commons-net:3.6'

Solution 2

There is no Android API to get you such a time. The user can always change the device time, nothing you can do about that.

Your best bet would be to run a server with a webservice, from which you can get the time. Since you control the server, you can try to ensure it returns the correct time.

Comments

[androidevil]

In my case, the valid timestamp was found using: timeInfo.getMessage().getReceiveTimeStamp().getTime()

[Stefano]

long returnTime = timeInfo.getMessage().getReceiveTimeStamp().getTime();

[Prashanth Debbadwar]

can we use joda time lib?

[Opiatefuchs]

older post, but it´s important here: Stefano is right. If getting time like showed in the post, it returns (described in API) ...time message packet was received by local machine . It seems that this returns the device time, I tried it. But if you use timeInfo.getMessage().getReceiveTimeStamp().getTime() , you get (described in API) ...the receive time as defined in RC_1305 which is the net time no matter what is defined in device..

[f.trajkovski]

Even if you use this method, changing the time on the phone will cause the NTPUDPClient to give you that time instead of the time from the host.