Php Date

Bonjour,

J'aimerais faire un système de date d'échéance sous Laravel mais je n'y arrive pas voici mon code.

Table

<?php

use Illuminate\Support\Facades\Schema;
use Illuminate\Database\Schema\Blueprint;
use Illuminate\Database\Migrations\Migration;

class CreateUsersTable extends Migration
{
    /**
     * Run the migrations.
     *
     * @return void
     */
    public function up()
    {
        Schema::create('users', function (Blueprint $table) {
            $table->increments('id');
            $table->string('name');
            $table->string('firstname');
            $table->string('email')->unique();
            $table->date('birthday');
            $table->string('password');
            $table->rememberToken();
            $table->timestamps();
        });
    }

    /**
     * Reverse the migrations.
     *
     * @return void
     */
    public function down()
    {
        Schema::dropIfExists('users');
    }
}

ProfilController

<?php

namespace App\Http\Controllers;

use App\Http\Controllers;
use App\User;
use Carbon\Carbon;
use Illuminate\Contracts\Auth\Guard;
use Illuminate\Http\Request;
use Illuminate\Support\Facades\Auth;

class ProfilController extends Controller
{
    /**
     * Create a new controller instance.
     *
     * @return void
     */
    public function __construct()
    {
        $this->middleware('auth');
        $this->middleware('owner', ['only' => ['edit', 'update', 'getEditResource']]);
    }

    public function index($name, $firstname, $id)
    {
        $authinfo = Auth::user();
        $userinfo = User::where('name', $name)->where('firstname', $firstname)->where('id', $id)->firstorfail();

        if($authinfo->created_at >= date("Y-m-d H:i:s", strtotime("$authinfo->created_at +1 days"))){
            dd("Tu doit t'abonner");
        }else{
            dd("Tu est premium");
        }

        //return view('users.particulier.profil', compact('authinfo', 'userinfo'));

    }

    public function getEditResource($name, $firstname, $id)
    {
        return User::where('name', $name)->where('firstname', $firstname)->where('id', $id)->firstorfail();
    }

    public function edit()
    {

        $authinfo = Auth::user();
        return view('users.particulier.edit', compact('authinfo'));

    }

    public function update(Request $request)
    {
        $user = Auth::user();

        $this->validate($request, [
            'name' => 'required',
            'firstname' => 'required',
            'avatar' => "image"
        ]);

        $user->update($request->only('name', 'firstname'));
        $user->profil->update($request->only('job', 'about', 'avatar'));
        return redirect(route('profil', [strtolower(Auth::user()->name), strtolower(Auth::user()->firstname), Auth::id()]))->with('success', 'Votre profil à bien était modifié');
    }

}

Mon utilisateur sont create_at = 2017-11-13 20:57:06

Mon problème c'est que la date d'échéance ne marche pas !

Merci.