I created an application that starts the timer at a specific time, but the countdown does not work at the specified time.

package com.example.countdowntimer;

import androidx.announcement.RequiresApi;
import androidx.appcompat.app.AppCompatActivity;

import android.os.Build;
import android.os.Bundle;
import android.os.CountDownTimer;
import android.widget.TextView;

import java.text.ParseException;
import java.time.LocalDateTime;

public class MainActivity extensions AppCompatActivity{

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

    @RequiresApi(api=Build.VERSION_CODES.O)
    public void compareDate1()throws ParseException {

        LocalDateTimedate1 = LocalDateTime.parse("2020-02-7T10:48:00.000");
        LocalDateTimedate3 = LocalDateTime.now();

        if(date1.isAfter(date3)){
            CountDownTimer countDownTimer = new CountDownTimer (3600000, 1000) {
                @ Override
                public void onTick (long millisUntilFinished) {
                    int time=(int)millisUntilFinished/1000;
                    int time2 = (int) millisUntilFinished/60000;
                    int time3 = (int) millisUntilFinished/3600000;
                    (((TextView) findViewById(R.id.tv)) .setText("+time3+":"+time2+":"+time%60);
                }

                @ Override
                public void onFinish(){
                    ((TextView) findViewById(R.id.tv)) .setText("Finish";
                }
            }.start();
        }
    }
}