If you feel your time zone is incorrect, you can...

Click Edit Profile from top-right conner. Select Site Options tab and scroll down to "Timezone" list. select which timezone is right for you.

Then "Save" it. 

Thank you for yor instrucitons, but do I need to change the time zone?

No, it is not nesserary. But if you did not, you will see incorrect posting time on your message. For example: are you posted on 4:32 AM morning on your time zone? :-) 

I believe it is my time EST and your afternoon time, wrote might be comfuse. I think I should default this site as Taiwan time zone, not East coast of USA. Sorry !!!

Thank you for your reply.