Remove the model $dates property and register custom fields as datetime within the casts property. The $dates property was deprecated in Laravel 8 and removed in Laravel 10.

Before

public User extends Model
{
    protected $casts = [
        'id' => 'integer',
    ];
 
    protected $dates = [
        'created_at',
        'updated_at',
        'deleted_at',
        'expired_at'
    ];
 
    // ...
}

After

public User extends Model
{
    protected $casts = [
        'id' => 'integer',
        'expired_at' => 'datetime',
    ];
 
    // ...
}