Keep Coding

I got the following error while trying to insert bulk data in DB table.
> D:\wamp\www\laravel>php artisan tinker Psy Shell v0.5.2 (PHP 5.5.12 ΓÇö cli) by Justin Hileman
>>> factory(App\User::class, 100)->create(array('email', 'password', 'firstname','lastname', 'dob', 'phone', 'website', 'role_id')); Invalid ArgumentException with message 'A four digit year could not be found Data missing'.
Fillable fields in App\User
protected $fillable = ['email', 'password', 'firstname', 'lastname', 'dob', 'phone', 'website', 'role_id'];
Can someone tell me what might be going wrong?