Trying to get property of non-object pada laravel 5.8

selamat pagi,disini saya ada kendala dimana awalnya saya ingin melooping data Posts didalam home sesudah itu saya ingin membuat single page tetapi disini saya memanggil {slug} ketika saya coba terjadilah Trying to get property 'created_at' of non-object saya lampirkan pesan error dan kodenya ,trimakasih sudah mau membantu saya

ini pesan errornya

ini SiteControllernya :

<?php

namespace App\Http\Controllers;

use Illuminate\Http\Request;
use App\Siswa;
use App\User;
use App\Post;

class SiteController extends Controller
{
    public function home()
    {
        $posts = Post::all();
        return view('sites.home', compact('posts'));
    }

    public function singlepost($slug)
    {
        $posts = Post::where('slug', '=', $slug)->first();
        return view('posts.singlepage', compact('posts'));
    }

    public function register()
    {
        return view('sites.register');
    }


}

ini home.blade.php

@foreach ($posts as $post)
                        <div class="col-lg-3 col-md-6 single-blog">
                            <div class="thumb">
                                <img class="img-fluid" src="{{asset('/education')}}/img/b1.jpg" alt="">
                            </div>
                            <p class="meta">{{$post->created_at->format('d-M-Y')}}  |  By <a href="#">{{$post->user->name}}</a></p>
                            <a href="blog-single.html">
                                <h5>{{$post->title}}</h5>
                            </a>
                            <p>
                                {!!$post->content!!}
                            </p>
                            <a href="{{route('site.single.post',$post->slug)}}" class="details-btn d-flex justify-content-center align-items-center"><span class="details">Details</span><span class="lnr lnr-arrow-right"></span></a>
                        </div>
                        @endforeach