FWIW, Facebook did not use UTC when I was there. They used Pacific time everywhere, which was even worse. And half of the internal tools would convert to local

FWIW, Facebook did not use UTC when I was there. They used Pacific time everywhere, which was even worse. And half of the internal tools would convert to local time but the other half wouldn't. I just kept my work machine in Pacific time even though I'm in Eastern, so that compiling incident timelines (for example) would be less tedious and error-prone.