Poof! You're on Earth

[iancampbell]

Sailors used to use chronometers to tell what their longitude was by comparing things like sun rise and sunset time to a clock set to GMT. The difficulty in making a clock that accurate that worked on a rocking boat was significant, leading to some really neat engineering:
https://en.wikipedia.org/wiki/Marine_chronometer

Indeed. The problem with that, in this scenario, is that longitude measurement by comparing local time to GMT only works if you have a chronometer set to GMT in the first place - which, in this scenario, you don't.