<?php

namespace App;

use Illuminate\Database\Eloquent\Model;

class Milestone extends Model
{

  public $timestamps = false;

  protected $fillable = [
      'name','description','start_at','due_at','end_at',
  ];

  public function tickets()
  {
      return $this->hasMany('App\Ticket');
  }
}

<?php

namespace App;

use Illuminate\Database\Eloquent\Model;

class Milestone extends Model
{
  public function tickets()
  {
      return $this->hasMany('App\Ticket');
  }
}

--- 
+++ 
@@ -6,6 +6,13 @@
 
 class Milestone extends Model
 {
+
+  public $timestamps = false;
+
+  protected $fillable = [
+      'name','description','start_at','due_at','end_at',
+  ];
+
   public function tickets()
   {
       return $this->hasMany('App\Ticket');
Add fillable options to milestone
