It's a sci-fi game where you can travel between multiple star systems in less than a day, with countless sentient species traveling between them. It's easy to imagine that sense of time would be a difficult thing to establish using visual queues outside of ones own personal quarters. Looking at international trade today, it's likely some sort of universal clock would be used as a means of keeping track of relative time, and individuals would set their own sleep schedules rather than rely on whatever the day/night cycle of the local planet is. Much like Modern cities, it's doubtful that any space-age society would really have much "down time" that such a thing would require. So, like Dark67titan said: there's a clock. Realistically, I think that's the best you'd get, at least in text-based game where survival isn't a major concern. Things like individual day/night cycles, seasons, how they relate to eachother, etc. would be interesting, but...is it worth it to edit a large number of room descriptions to account for those variables, when they shouldn't have much of an effect on their society, let alone your play experience? Maybe for a specific planet down the line, but it'd need a good reason considering the amount of inconveniences that could pose involving quests or scenes that rely on specific amounts of time time passing. The dark sidebar idea could be an interesting addition to such a planet, though.
And then there's the sleep issue: it seems to me like their society has plentifully available anti-aging medicine, nanobots that boost immune systems (of which Steele seems to have a highly advance version of), and vending machines that instantly give you boosts of energy that don't just seem like caffine blends, while there are clearly multiple organizations and corporations demonstrating that their society has a growing mastery of genetics - all of which help to alleviate the usual problems. I'm just saying: It could be entirely possible that Steele wouldn't actually need to sleep so long as they aren't pushed too hard. Things like the sore status effects, health regeneration, dreams, and yes, even level-ups, requiring prolonged rest/sleep actually makes a lot of sense, at least with all the info I've found.
