Load Helper Classes in Laravel 5.1

I have many helper classes in my app/Helpers directory.

Let use DateHelper.php as example.

]1

Then, I have HelperServiceProvider.php

<?php

namespace App\Providers;

use Illuminate\Support\ServiceProvider;

class HelperServiceProvider extends ServiceProvider
{
    /**
     * Bootstrap the application services.
     *
     * @return void
     */
    public function boot()
    {
        //
    }

    /**
     * Register the application services.
     *
     * @return void
     */
    public function register()
    {
        foreach (glob(app_path().'/Helpers/*.php') as $filename){
            require_once($filename);
        }
    }
}

Then, I register it in my 'providers' array in config/app.php

'App\Providers\HelperServiceProvider',

Then, I create an alias

'DateHelper'  => App\Helpers\DateHelper::class,

Then, I tried to call it

{{ DateHelper::f1($visitor->created_at) }}

Then, I run composer dumpauto

I kept getting

FatalErrorException in 7a9854b6de232272901da9bc64800d54 line 38:
Class 'DateHelper' not found

Can someone please tell me what did I do wrong ?

via Chebli Mohamed