Laravel - Model Default value

I have a table like it-

http://ift.tt/1VuthSP

And model for it is like this-

<?php

namespace App;

use Illuminate\Database\Eloquent\Model;
use Illuminate\Http\Request;

class WebinarLiveAttenders extends Model
{
    protected $table = 'webinar_live_attenders';
    protected $primaryKey='id';
    protected $fillable = array('webinar_id','ip','last_update');
    public $timestamps=false;

    public function webinars()
    {
        return $this->hasOne('App\Webinar');
    }
}

I am running a query like this-

public function post_update_user_status()
{
    //Request::getClientIp();
    $requestData = Request::all();
    $date = new DateTime;
    $formatted_date = $date->format('Y-m-d H:i:s');

    $user_status = WebinarLiveAttenders::firstOrNew([
                                                        'webinar_id' => $requestData['uuid'],
                                                        'ip'         => Request::getClientIp()
                                                    ]);
    $user_status->last_update = $formatted_date;
    $user_status->save();
    return 'Done';
}

Problem is I am getting time_on=0 always.

But I want it to be the time of creation.

I can't use timestamps here.

Can anyone please help?

via Chebli Mohamed