This is a great and very useful plugin. However, I have found that some IP addresses in the MaxMind database don't include a timezone and this is causing the plugin to produce an unhandled exception.
As this only happens with a very small number of IP addresses, it could be causing seemingly random errors to some site visitors.
I have patched this locally, but I can't find a GitHub repo for this plugin in order to submit a pull request. Is there one?