Star Wars never really explores the cool time-keeping situations that you can end up with in a society that spans multiple planets:
planets with no moon that don’t have a time increment between days and years
planets with a dozen moons where understanding their cycles involves university courses
multi-planet star systems where the position of the other planet features prominently in calendar systems
tidally locked planets with no days (or years, really, because even though they’re orbiting a star they wouldn’t have significant changes in seasons)
and not only do they not have days or years, they have no cultural concept of those things and are bewildered by the rest of the galaxy’s obsession with measuring time
planets with years so long that they’re useless as a way of measuring age, so people give their age in months instead
planets with like 6 hour days where people are used to sleeping frequently for only a couple hours at a time
the space equivalent of jetlag involves adjusting to a new day length, not just a new time zone
when two planets have slightly different day lengths, the days shift relative to each other, so if you travel frequently between two such planets, sometimes the days line up perfectly and sometimes you have to deal with 12 hours of “jet”lag
And there are tons of interesting cultural implications that go along with using Coruscant time as a standard throughout the galaxy:
standard Coruscant dates have basically no correlation to seasons on planets with different year lengths, so to even guess at the weather during a historical date given in standard time you need to do calculations
everyone has a different age in local years and standard years, and a different birthday
some planets have days much longer or shorter than standard days, so your standard birthday might be spread over a few local days or vice versa
stuff like being old enough to drive – it tends to go in round numbers of local years, so even on planets where the rule is “about 18 standard”, you have some planets where it’s actually 17.36 standard years, or 19.1, or whatever works out nicely in local years
planets that follow Coruscant standard time and totally ignore natural phenomena on their own planets
up to and including days – they force themselves into sleep cycles with nothing to do with the sun rising and setting
planets that refuse to use standard time even in official settings, and pilots hate having to travel there because the space port is always chaotic because no one knows what time it is
the Separatists try to switch to another time system than Coruscant standard and it’s a total mess but it would be embarrassing to switch back
the Rebellion learns their lesson from this and doesn’t try to change the standard time system even though the New Republic government is no longer based on Coruscant
people pay less and less attention to standard time as you get farther from the core
planets with similar natural time cycles to Coruscant have more prosperous economies and produce more prominent and successful people, although the effect is subtle enough that it goes unnoticed until someone randomly decides to check for correlation
On some planets, moons orbit so close that they’re not visible above certain latitudes (for example, you can’t see Mars’ moon Phobos near the north/south poles of the planet). Imagine cultures that develop separate time systems, based on the moon(s) they can see, and visitors to the planet hate trying to remember if a month in this region is 12 or 45 days long
Or planets with multiple moons with vastly different orbital altitudes, where one orbit is used to measure a week (or some other time interval) and the other a month (again with Mars, Phobos orbits ~3 times a day, which could maybe be used to denote something like a work day)
Also have no idea how a time-keeping system would develop on a moon (like Endor) instead of a planet
Presumably not every alien in the galaxy shares the same circadian rhythm, so how does that factor in when deciding on a time system for a space ship/station? Coruscant standard time is probably great for humans, but what about others? Do the Mon Calamari cruisers have their own internal time system based off their home planet, that hopelessly confuses the human members of the rebellion stationed there?
Time dilation?!???
