Thank's for the response. I have changed the time offset from '0' to '10'. It did change the existing data time field to my local time, but it did not adjust display time to my local time. New entry also not affected by the time offset.
Currently my web published in a webhosting service company which is far away from my location. I'd like to adjust the time appears on my guestbook to be the same as my current location (instead of server location).