I am submitting a user last seen on Firebase Realtime Database and before setting value at firebase database I am generating a log with timestamp by System.currentTimeMillis() but when I compare it with logcat and database timestamp it submits a different timestamp on the server.

Look at the logcat it shows the correct timestamp and it should be on the server too

Disconnect with the firebase server 
Offline Time 5:01 pm 1639308715905

Firebase Realtime Database Value of Timestamp

1639308009264

Both Values are different that's how I get wrong last seen of the user

1639308715905 - App one 
1639308009264 - Server One

The code I am using for log and to set a value on the server.

public class MainActivity extends AppCompatActivity {

    public static final String TAG = "Main Activity";
   
    FirebaseDatabase DatabaseInstance;
    DatabaseReference infoConnected;
    



    @Override
    protected void onResume() {
        super.onResume();
        Log.d(TAG, "On Resume Running");        
        DatabaseInstance.goOnline();
        
    }


    @Override
    protected void onStop() {
        super.onStop();
        Log.d(TAG, "ON STOP CALLING");
        DatabaseInstance.goOffline();


    }


    @Override
    protected void onCreate(@Nullable Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        DatabaseInstance = FirebaseDatabase.getInstance(); // Single Instance
        infoConnected = DatabaseInstance.getReference(".info/connected"); // To check firebase connection state
        initialiseOnlineStatus();

        setContentView(R.layout.main);
    }
        



    
    private void initialiseOnlineStatus() {
        final DatabaseReference Online = DatabaseInstance.getReference("Users/" + userID + "/Online");
        final DatabaseReference lastOnline = DatabaseInstance.getReference("Users/" + userID + "/lastSeen");


        infoConnected.addValueEventListener(new ValueEventListener() {
            @Override
            public void onDataChange(@NonNull DataSnapshot dataSnapshot) {
                boolean connected = dataSnapshot.getValue(Boolean.class);

                if (connected) {
                    Online.setValue(Boolean.TRUE);
                    lastOnline.removeValue();

                    Log.d(TAG, "Connected To Firebase Server ");
                } else {
                    Log.d(TAG, "Disconnect with firebase server ");
                    Online.onDisconnect().setValue(Boolean.FALSE);
                    String offlineTime = String.valueOf(System.currentTimeMillis());
                    Log.d(TAG, "Offline Time " + App_Functions.getLocalDeviceTimestamp(Long.parseLong(offlineTime)) + " " + offlineTime); // Get local device time from milliseconds
                    lastOnline.onDisconnect().setValue(offlineTime);
                    
                }

            }

            @Override
            public void onCancelled(@NonNull DatabaseError databaseError) {

            }
        });


    }



} 

Update: I noticed that the last timestamp (generated by an app) is uploading not the current one, I really don't understand how my last seen is not updating by the current timestamp. Please check gist too for the complete code

I also noticed that on the launch of my activity, the firebase function call twice, first with value boolean connected = dataSnapshot.getValue(Boolean. class); false than true. So with the false value, I am getting the first timestamp which should not update when activity onStop calls and when the app calls onStop it updates the timestamp which was first created on app launch.