Audit Trail - To store current Date

Hello Everyone,

        I am using Audit Trail module of YII for audit logs. I have a user table in which one field is user_created_date as Datetime. When I create a new record, in this user_created_date field has the current time stamp. For that I write a code in controller's actionCreate as below : 

$model->user_created_date=new CDbExpression(‘NOW()’);

So, when user created, in user table it stores curremt time stamp. It is working fine.

But when Audit trail stamps the log in the field "new_value" in audit log table, it stores text "now()" instead of current timestamp. Otherthan this field gives the proper logs in audit log.

I want to store mysql date to store in time stamp not the php date. Waiting for your reply.