To clarify, these monk maps do not detect your location from your IP address.

Jcwren defined a protocol of location markers you could place to your homenode “biblography” by hand, and his monk map and nearest monk tables scanned homenodes for such markers. This was documented on his statistics pages, which don't work anymore. The format is magic html comments like <!-- location:latitude=38.08.19.5,longitude=4.50.31.2 --> which gives your geograpical coordinates in degrees, minutes, and seconds, with positive numbers meaning north and east respectively.

Castaway's map also used these comments, as well as recognizing geographical names you put to your location field of your homenode, and using the timezone you set in your settings as a fallback.