If user change date and time in device then how to get current date and time in android?

Question

If any user change date and time in his/her device then how to get current date and time which is actually running. I am working on a project that use current date as the start date so if user change his/her date as he want then its custom date will be my start date in place of that i want to current date if device date is before of after.

Ex. Now current date is 8 Aug 2015 then user change his/her device date as 20 Aug 2015 then how I can get actual date which is 8 Aug 2015? Thank you in advance...

Answer 1

Connection to NTP Server:

import android.os.AsyncTask;

import java.net.DatagramPacket;
import java.net.DatagramSocket;
import java.net.InetAddress;


public class NTPUTCTime {
    private static final String TAG = "SntpClient";

    private static final int RECEIVE_TIME_OFFSET = 32;
    private static final int TRANSMIT_TIME_OFFSET = 40;
    private static final int NTP_PACKET_SIZE = 48;

    private static final int NTP_PORT = 123;
    private static final int NTP_MODE_CLIENT = 3;
    private static final int NTP_VERSION = 3;

    // Number of seconds between Jan 1, 1900 and Jan 1, 1970
// 70 years plus 17 leap days
    private static final long OFFSET_1900_TO_1970 = ((365L * 70L) + 17L) * 24L * 60L * 60L;

    private long mNtpTime;

    public boolean requestTime() {
        try {
            new AsyncTask<Void, Void, Boolean>() {
                @Override
                protected Boolean doInBackground(Void... voids) {
                    try {
                        DatagramSocket socket = new DatagramSocket();
                        socket.setSoTimeout(1000);
                        InetAddress address = InetAddress.getByName("pool.ntp.org");
                        byte[] buffer = new byte[NTP_PACKET_SIZE];
                        DatagramPacket request = new DatagramPacket(buffer, buffer.length, address, NTP_PORT);
                        buffer[0] = NTP_MODE_CLIENT | (NTP_VERSION << 3);

                        writeTimeStamp(buffer, TRANSMIT_TIME_OFFSET);

                        socket.send(request);

                        // read the response
                        DatagramPacket response = new DatagramPacket(buffer, buffer.length);
                        socket.receive(response);
                        socket.close();

                        mNtpTime = readTimeStamp(buffer, RECEIVE_TIME_OFFSET);
                    } catch (Exception e) {
                        //  if (Config.LOGD) Log.d(TAG, "request time failed: " + e);
                        e.printStackTrace();
                        return false;
                    }
                    return true;
                }
            }.executeOnExecutor(AsyncTask.THREAD_POOL_EXECUTOR).get();

        } catch (Exception e) {
            //  if (Config.LOGD) Log.d(TAG, "request time failed: " + e);
            e.printStackTrace();
            return false;
        }

        return true;
    }


    public long getNtpTime() {
        return mNtpTime;
    }


    /**
     * Reads an unsigned 32 bit big endian number from the given offset in the buffer.
     */
    private long read32(byte[] buffer, int offset) {
        byte b0 = buffer[offset];
        byte b1 = buffer[offset + 1];
        byte b2 = buffer[offset + 2];
        byte b3 = buffer[offset + 3];

        // convert signed bytes to unsigned values
        int i0 = ((b0 & 0x80) == 0x80 ? (b0 & 0x7F) + 0x80 : b0);
        int i1 = ((b1 & 0x80) == 0x80 ? (b1 & 0x7F) + 0x80 : b1);
        int i2 = ((b2 & 0x80) == 0x80 ? (b2 & 0x7F) + 0x80 : b2);
        int i3 = ((b3 & 0x80) == 0x80 ? (b3 & 0x7F) + 0x80 : b3);

        return ((long) i0 << 24) + ((long) i1 << 16) + ((long) i2 << 8) + (long) i3;
    }

    /**
     * Reads the NTP time stamp at the given offset in the buffer and returns
     * it as a system time (milliseconds since January 1, 1970).
     */
    private long readTimeStamp(byte[] buffer, int offset) {
        long seconds = read32(buffer, offset);
        long fraction = read32(buffer, offset + 4);
        return ((seconds - OFFSET_1900_TO_1970) * 1000) + ((fraction * 1000L) / 0x100000000L);
    }

    /**
     * Writes 0 as NTP starttime stamp in the buffer. --> Then NTP returns Time OFFSET since 1900
     */
    private void writeTimeStamp(byte[] buffer, int offset) {
        int ofs = offset++;

        for (int i = ofs; i < (ofs + 8); i++)
            buffer[i] = (byte) (0);
    }

}

Or you can use this library

https://github.com/instacart/truetime-android