As HT says it works it out from the IP address you are currently accessing the site from. We do occasionally have a few oddities where it shows a country you aren't in, but that's usually down to a proxied internet connection.....change the flag on my profile (the flag that shows up next to my username on posts)?
Yep, @Gail is online from the Netherlands when she is at work in the UK.so it could be a common thing?