Service

package com.example.root.myapplication1;

import android.app.Notification;
import android.app.NotificationManager;
import android.app.PendingIntent;
import android.app.Service;
import android.content.Context;
import android.content.Intent;
import android.os.IBinder;
import android.support.v4.app.NotificationCompat;

import java.util.Calendar;
import java.util.Date;
import java.util.concurrent.TimeUnit;

public class Alarms extends Service {
    DBPlanner dbPlanner;
    Context context;
    Calendar calendar;
    NotificationManager notificationManager;
    @Override
    public int onStartCommand(Intent intent, int flags, int startId) {

        task();
        return super.onStartCommand(intent, flags, startId);
    }

    @Override
    public void onCreate() {
        dbPlanner=new DBPlanner(getApplicationContext());
        context=this;

        super.onCreate();
    }

    @Override
    public void onDestroy() {
        super.onDestroy();
    }

    @Override
    public IBinder onBind(Intent intent) {
        return null;
    }
    void task(){

        new Thread(new Runnable() {
            @Override
            public void run() {

                while (true){
                    calendar=Calendar.getInstance();
                    Integer hours=calendar.get(Calendar.HOUR_OF_DAY);
                    Integer minutes=calendar.get(Calendar.MINUTE);
                    String month,day;
                    if(calendar.get(Calendar.MONTH)<=9){
                        month="0"+calendar.get(Calendar.MONTH);
                    }else{
                        month=calendar.get(Calendar.MONTH)+"";
                    }
                    if(calendar.get(Calendar.DAY_OF_MONTH)<=9){
                        day="0"+calendar.get(Calendar.DAY_OF_MONTH);
                    }else{
                        day=calendar.get(Calendar.DAY_OF_MONTH)+"";
                    }
                    Plans plan=dbPlanner.find(hours,minutes,day+"/"+month+"/"+calendar.get(Calendar.YEAR));
                    if(plan.getPlan()!=null){
                        NotificationCompat.Builder builder = new NotificationCompat.Builder(getApplicationContext())
                                        .setSmallIcon(R.mipmap.ic_launcher)
                                        .setContentTitle("Напоминание")
                                        .setContentText(plan.getPlan());
                        Notification notification = builder.build();
                        notification.flags |=Notification.FLAG_AUTO_CANCEL;
                        NotificationManager notificationManager =
                                (NotificationManager) getSystemService(NOTIFICATION_SERVICE);

                        notificationManager.notify(1, notification);


                    }
                    try {
                        TimeUnit.SECONDS.sleep(60);
                    } catch (InterruptedException e) {
                        e.printStackTrace();
                    }
                }
            }
        }).start();
    }
}