public class MainActivity extends Activity {

Button btn;

@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);

btn = (Button) findViewById(R.id.btn);
btn.setOnClickListener(new View.OnClickListener() {
    @Override
    public void onClick(View v) {
        PasteData();
    }
});
}

private void  PasteData(){
Calendar c = Calendar.getInstance();
int dp = c.get(Calendar.DAY_OF_MONTH);
final int mp = c.get(Calendar.MONTH);
int yp = c.get(Calendar.YEAR);

DatePickerDialog dpd = new DatePickerDialog(MainActivity.this, AlertDialog.THEME_HOLO_DARK, new DatePickerDialog.OnDateSetListener() {
    @Override
    public void onDateSet(DatePicker view, int year, int month, int dayOfMonth) {
        Intent i = new Intent(MainActivity.this, SecondActivity.class);
        i.putExtra("DayB",dayOfMonth);
        i.putExtra("MonthB",month);
        i.putExtra("YearB",year);
        btn.setText(dayOfMonth+"/"+(month+1)+"/"+year);
    }
},dp,mp,yp);
c.add(Calendar.SECOND, 1);
dpd.getDatePicker().setMaxDate(c.getTimeInMillis());
dpd.getDatePicker().setMinDate(0);
dpd.show();
}
}

public class SecondActivity extends Activity {

TextView tvAge;

@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_second);

Bundle BB = this.getIntent().getExtras();

int d = BB.getInt("DayB");
int m = BB.getInt("MonthB");
int y = BB.getInt("YearB");
CalculateAge(d,m,y);
}

private void CalculateAge (int dayBd, int monthBd, int yearBd){
Calendar c = Calendar.getInstance();
int ActDay = c.get(Calendar.DAY_OF_MONTH);
int ActMonth = c.get(Calendar.MONTH);
int ActYear = c.get(Calendar.YEAR);

int age = ActYear-yearBd;
if ( monthBd>ActMonth){
    age--;
}else if (ActMonth==monthBd){
    if (dayBd>ActDay){
        age--;
    }
}

tvAge = (TextView) findViewById(R.id.tvAge);
tvAge.setText(age);
}