void CarregaSegundaTela(){
               setContentView (R.layout.tela2);//inicia a segunda tela

               Button btvolt = (Button)findViewById(R.id.btvoltar);//inicia o botao voltar
               btvolt.setOnClickListener(new View.OnClickListener() {
                   
                    @Override
                    public void onClick(View arg0) {
                        onCreate(null);}//chama a primeira tela
               }
               );
               
               MostraTempo();
               Button btat = (Button)findViewById(R.id.tb1);
               btat.setOnClickListener(new View.OnClickListener() {
                @Override
                public void onClick(View v) {
                    MostraTempo();
                }
            });
               
    }//Carregar a segunda tela
           
   
    public void MostraTempo(){
        final TextView ianos, imeses, idias, ihoras, iminutos, isegundos;
        ianos = (TextView) findViewById(R.id.ano);
        imeses = (TextView) findViewById(R.id.mes);
        idias = (TextView) findViewById(R.id.dia);
        ihoras = (TextView) findViewById(R.id.hora);
        iminutos = (TextView) findViewById(R.id.minuto);
        isegundos = (TextView) findViewById(R.id.segundo);
       
       
        final int SegMinuto=60;
        int SegHora=3600, SegDia=86400, SegMes=2628000, SegAno=31536000; //Conversões

 
        Calendar dataInicio = Calendar.getInstance();
        // Data Desejada
        dataInicio.set(2000, Calendar.JUNE, 14, 10,0,54);
       
        // Data de hoje
        Calendar dataFinal = Calendar.getInstance();
 
        // Calcula a diferença entre hoje e da data de inicio
        long diferenca = dataFinal.getTimeInMillis() -
                         dataInicio.getTimeInMillis();
       
        long diferenca2 = diferenca / 1000;
       
        final long Resto=diferenca2%SegAno;
        long Resto2=diferenca2%SegMes;
        long Resto3=diferenca2%SegDia;
        final long Resto4=diferenca2%SegHora;
        long Resto5=diferenca2%SegMinuto;
        //System.out.println(""+diferenca2/SegAno+ " Ano(s) " +Resto/SegMes +" Meses(s) " +Resto2/SegDia + " Dias(s)" + Resto3/SegHora + " Hora(s)" + Resto4/SegMinuto + "Minuto(s)" + Resto4%SegMinuto + "Segundo(s)");

        ianos.setText(String.valueOf(diferenca2/SegAno));
        imeses.setText(String.valueOf(Resto/SegMes));
        idias.setText(String.valueOf(Resto2/SegDia));
        ihoras.setText(String.valueOf(Resto3/SegHora));
        iminutos.setText(String.valueOf(Resto4/SegMinuto));
        isegundos.setText(String.valueOf(Resto4%SegMinuto))
         
         
    }

package com.rafaeldecker.timer;

import java.util.Calendar;

import android.os.Bundle;
import android.os.Handler;
import android.app.Activity;
import android.widget.TextView;

public class MainActivity extends Activity {

    private Handler handler;

    private static final int ONE_MINUTE_IN_SECONDS = 60;
    private static final int ONE_HOUR_IN_SECONDS = 3600;
    private static final int ONE_DAY_IN_SECONDS = 86400;
    private static final int ONE_MONTH_IN_SECONDS = 2628000;
    private static final int ONE_YEAR_IN_SECONDS = 31536000;

    private Calendar startDate;
    private Calendar todayDate;
    private long remainingTime;

    /**
     * VIEWS
     */
    private TextView yearTextView;
    private TextView monthTextView;
    private TextView dayTextView;
    private TextView hourTextView;
    private TextView minuteTextView;
    private TextView secondTextView;

    @Override
    public void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);

        setupViews();

        setupTimer();

        updater();
    }

    private void setupViews() {
        setContentView(R.layout.activity_main);

        handler = new Handler();

        yearTextView = (TextView) findViewById(R.id.years);
        monthTextView = (TextView) findViewById(R.id.months);
        dayTextView = (TextView) findViewById(R.id.days);
        hourTextView = (TextView) findViewById(R.id.hours);
        minuteTextView = (TextView) findViewById(R.id.minutes);
        secondTextView = (TextView) findViewById(R.id.seconds);
    }

    private void setupTimer() {
        startDate = Calendar.getInstance();
        startDate.set(2000, Calendar.JUNE, 14, 10, 0, 54);

        todayDate = Calendar.getInstance();

        remainingTime = (todayDate.getTimeInMillis() - startDate.getTimeInMillis()) / 1000;
    }

    public void updater() {

        if (remainingTime > 0) {
            // Decrease the time in one second
            remainingTime -= 1;

            updateDisplay();

            Runnable notification = new Runnable() {
                public void run() {
                    updater();
                }
            };

            // It will be called each 1 second
            handler.postDelayed(notification, 1000);
        }

    }

    private void updateDisplay() {
        long yearDivisionRest = remainingTime % ONE_YEAR_IN_SECONDS;
        long monthDivisionRest = remainingTime % ONE_MONTH_IN_SECONDS;
        long dayDivisionRest = remainingTime % ONE_DAY_IN_SECONDS;
        long hourDivisionRest = remainingTime % ONE_HOUR_IN_SECONDS;

        yearTextView.setText("" + (remainingTime / ONE_YEAR_IN_SECONDS));
        monthTextView.setText("" + (yearDivisionRest / ONE_MONTH_IN_SECONDS));
        dayTextView.setText("" + (monthDivisionRest / ONE_DAY_IN_SECONDS));
        hourTextView.setText("" + (dayDivisionRest / ONE_HOUR_IN_SECONDS));
        minuteTextView.setText("" + (hourDivisionRest / ONE_MINUTE_IN_SECONDS));
        secondTextView.setText("" + (hourDivisionRest % ONE_MINUTE_IN_SECONDS));
    }

}