OK.  My mistake.  It is not UTC.  The server that holds this website is at a location 16 hours ahead of Canada/Pacific.  I bet it is in Hong Kong. 
 
The reason why 'if I view the site as a guest it says that this thread was started at 4:23 PM and if I'm logged in it says 9:23 AM (which is correct). ' is that ... 
 
When you created the thread, the time '2010-02-25_15:31' was stamped onto your thread.  (It was 2010-02-24_23:31 in HK) 
 
When you view the thread as owner, it shows the timestamp of your thread.   
 
When you view as a guest, since the server doesn't know where your timezone is, it simply shows the server's time. 
		
	
		
		
		
		
		
	
		
		
	
	
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