Android版は何日生きましたか

package com.example.agetestwithandroid;

import java.util.Calendar;
import java.util.Date;
import java.util.GregorianCalendar;

import android.os.Bundle;
import android.app.Activity;
import android.view.Menu;
import android.view.View;
import android.view.View.OnClickListener;
import android.widget.Button;
import android.widget.DatePicker;
import android.widget.TextView;
import android.widget.DatePicker.OnDateChangedListener;

public class MainActivity extends Activity {

	private TextView tvNow,tvBirth,tvLife;
	private DatePicker mDatePicker;
	private Button btn;
	 int userYear = 0;
 	int userMonth = 0;
 	int userDay = 0;
 	long now ;
 	long userAge;
 	long days;
 	long howManyDays;
    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);

        mDatePicker = (DatePicker) findViewById(R.id.personalinfo_body_birthday);
        btn = (Button) findViewById(R.id.btn);

		Calendar calendar = Calendar.getInstance();
		int year = calendar.get(Calendar.YEAR);
		int month = calendar.get(Calendar.MONTH);
		int day = calendar.get(Calendar.DAY_OF_MONTH);
		
		
		mDatePicker.init(year, month, day, new OnDateChangedListener()
		{
			@Override
			public void onDateChanged(DatePicker view, int year,
					int monthOfYear, int dayOfMonth)
			{
				System.out.println("========   "+year+"-"+(monthOfYear+1)+"-"+dayOfMonth);
				Calendar birth = new GregorianCalendar();
				birth.set(year, monthOfYear, dayOfMonth);//       0     ，  ：      +1 =     ，  ：       =     -1
				
				
				Date date = new Date();
				date = birth.getTime();
				long time = date.getTime();//       long time = birth.getTime().getTime();
				System.out.println("======android======time="+time);
				
				long betTime = System.currentTimeMillis() - time;
				System.out.println("======android=========System.currentTimeMillis()="+System.currentTimeMillis());
				howManyDays = betTime/(24*3600*1000);
			}
		});
		
		btn.setOnClickListener(new OnClickListener()
		{
			@Override
			public void onClick(View v)
			{
				System.out.println("==========================    ===============      "+howManyDays+" ");
			}
		});
    }
    
}

レイアウトファイル

<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:tools="http://schemas.android.com/tools"
    android:orientation="vertical"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:paddingBottom="@dimen/activity_vertical_margin"
    android:paddingLeft="@dimen/activity_horizontal_margin"
    android:paddingRight="@dimen/activity_horizontal_margin"
    android:paddingTop="@dimen/activity_vertical_margin"
    tools:context=".MainActivity" >

   <DatePicker
            android:id="@+id/personalinfo_body_birthday"
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:calendarViewShown="false"
            android:layout_marginLeft="45dp"
            android:layout_marginTop="20dp" />
   <Button 
        android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:id="@+id/btn"
            android:text="       "
       />
</LinearLayout>