Right, it's defined as part of tzset(3), which node does some hackery to support Windows as well by the looks of it. I'd be curious to see if this does actually work under Windows, given that [node's own test default to CET](https://github.com/joyent/node/blob/master/test/simple/test-process-env.js#L23) to [match the code's default fallback when timezone detection fails](https://github.com/joyent/node/blob/master/deps/v8/src/platform-win32.cc#L433-434).