wezm.net/content/personal/2008/05/geohashing.html

<a href='http://xkcd.com/426/'><img src="http://www.wezm.net/wp-content/uploads/wezm.net/2008/05/geohashing-resized.png" alt="Geohashing xkcd comic" title="geohashing-resized" width="400" height="223" class="aligncenter size-full wp-image-24" /></a>

Randall Munroe proposed the awesomely geeky idea of geohashing via the xkcd <a href="http://xkcd.com/426/">comic</a> and <a href="http://blag.xkcd.com/2008/05/21/geohashing/">blag</a> recently. The idea basically involves using the MD5 hash of a date combined with the opening value of the Dow Jones Index for that date to derive a latitude and longitude relative to a (generally your own) location. 

However there is a problem for those of us residing in Australia (and other locations with a time zone significantly different from EST). With the Dow Jones Index operating on US time its not possible to determine a geohashed location in Australia until about 23:00 AEST for a given date. No doubt others have thought of this but I suggest we use the <a href="http://finance.yahoo.com/q?s=^AORD">All Ordinaries Index</a> instead. With that out of the way we just need some enterprising sole with some spare time to implement a version of the <a href="http://irc.peeron.com/xkcd/map/">map</a> based on this.

<strong>Update:</strong> More info on geohashing in Melbourne on the <a href="http://visibleprocrastinations.wordpress.com/2008/05/22/geohashing/">Visible Procrastinations</a> blog.

<strong>Another Update:</strong> Using the Dow on the weekend works well though. As over the weekend everyone is more or less synced to the same index.

<strong>Final Update:</strong> The <a href="http://blag.xkcd.com/2008/05/23/geohashing-followup-change-to-algorithm-for-europe-africa-asia-australia/">xkcd blag has a follow up article</a> that clarifies the behaviour for Europe, Asia and Australia. It boils down to using the previous day's Dow Jones Index.