In Voyager, Season 1, Episode 6 (Eye of the Needle), Captain Janeway communicates with a Romulan vessel in the Alpha quadrant via a probe relay in a wormhole.
At the end of the conversation they have while she's in her quarters, the Romulan says "good night".
How did the Romulan know that it was night time on Voyager? (I know the answer now... but my more general question still stands.)
Do the Romulans follow the same day/night cycle as Starfleet? Do any of the humanoid species in Star Trek follow a different day/night cycle?