Alexa guesses traffic based on people who use their Alexa toolbar as a statistical sample. To get an accurate view of the traffic, use quantcast:
http://www.quantcast.com/wrongplanet.net
There is utterly no point in posting your time zone - although you could always post your whole address, if you wanted people to know where you lived.
The post time is perfectly adequate - and no way could you "compensate" to obtain any useful data from any time and/or time zone embedded in the post.
Also... to gather a year's graph, you could just visit this site four times:
http://www.alexa.com/siteinfo/wrongplanet.netNB. You do need to "compensate" for the many web crawlers that are present among the "Online Now: 652". In fact, only the "Members: 125" is vaguely reliable.