日历选择器上默认的时间不是手机系统的时间， 是随机的一个时间，是正常的吗？看老师的是手机默认时间啊

代码：

package com.example.hys.datatimepick;

import android.app.DatePickerDialog;
import android.os.Bundle;
import android.support.v7.app.AppCompatActivity;
import android.widget.DatePicker;
import android.widget.TimePicker;

import java.util.Calendar;

public class MainActivity extends AppCompatActivity {

   private TimePicker tp;
   private DatePicker dp;
   private Calendar cal;
   private int year;
   private int month;
   private int day;
   private int hour;
   private int minute;
   private int second;

   @Override
   protected void onCreate(Bundle savedInstanceState) {
       super.onCreate(savedInstanceState);
       setContentView(R.layout.activity_main);
       //获取日历的对像
       cal = Calendar.getInstance();
       //获取时间
       year = cal.get(Calendar.YEAR);
       month = cal.get(Calendar.MONTH)+1;
       day = cal.get(Calendar.DAY_OF_MONTH);
       hour = cal.get(Calendar.HOUR_OF_DAY);
       minute = cal.get(Calendar.MINUTE);
       second = cal.get(Calendar.SECOND);
       setTitle(year+"-"+month+"-"+day+" "+hour+":"+minute+":"+second);
       dp = (DatePicker) findViewById(R.id.datePicker);
       tp = (TimePicker) findViewById(R.id.timePicker);
       //初始化datepicker
       dp.init(year, cal.get(Calendar.MINUTE), day, new DatePicker.OnDateChangedListener() {
           @Override
           public void onDateChanged(DatePicker view, int year, int monthOfYear, int dayOfMonth) {
               setTitle(year+"-"+(monthOfYear+1)+"-"+dayOfMonth);
           }
       });
       tp.setOnTimeChangedListener(new TimePicker.OnTimeChangedListener() {
           @Override
           public void onTimeChanged(TimePicker view, int hourOfDay, int minute) {
               setTitle(hourOfDay+":"+minute);
           }
       });


       new DatePickerDialog(this, new DatePickerDialog.OnDateSetListener() {
           @Override
           public void onDateSet(DatePicker view, int year, int monthOfYear, int dayOfMonth) {
               setTitle(year+"-"+(monthOfYear+1)+"-"+dayOfMonth);
           }
       },year, cal.get(Calendar.MINUTE),day).show();


   }
}