A long time ago I did a quick survey of Satoshi's posts just for fun and found that he seemed to be posting with a US time zone.

Here is the graph (X axis are hours, Y axis is posts, times are GMT):



And the data itself:

[[0,32],[1,23],[2,15],[3,10],[4,9],[5,3],[6,3],[7,0],[8,0],[9,1],[10,0],[11,0],[12,3],[13,5],[14,14],[15,18],[16,46],[17,65],[18,65],[19,43],[20,42],[21,55],[22,46],[23,42]]

As you can see the night dip is between 6-11am GMT, so assuming this person sleeps at night, he should live in GMT-5 to GMT-7 somewhere which is the Americas.

Anyway, this was just a quick fun thing I did way back when. The reason I'm posting it now is that somebody dug up my IRC logs where I promised that I'd post it on the forums.