In orbit, time doesn't really matter unless an administrative office is closed. If the high port is geosynchronous (ostensibly to the associated downport), then the two are likely bound together in terms of what "day" and "night" mean.
Perhaps someone with Submarine or ship experience can talk about "Zulu" time, which as I understand it, is the US military clock schedule, and whether they actually "stay" on Zulu time on land, or simply adjust their watches to normal time and be done with it.
Universal time is not particularly important, especially since Jump is random. Having precise time doesn't really buy you anything. Rather, you jump in (however long it took), note the duration, then convert your clocks to the local system time (perhaps the main starport time), and then start working on jump lag and day lag. Jump lag is simply dealing with time offset (like a time zone here), day lag is dealing with the different lengths of physical days on the individual planets.
It's easy to see how orbital facilities in a system would all be on the same clock and day/night cycle, again, likely tied to the main planet. They need to pick "something", may as well pick the time that most of the population are using. Dual mode clocks will be quite common to correlate different time areas, and, perhaps, for the lowest of default cases, those folks in the lone system doing nothing but asteroid mining, there might be an Imperial standard day (or whatever).
But, simply, if you have a populated planet, that's not tide locked, that's going to be the dominant clock of the system, as they do most of the work, and beings bind to the day/night cycle, so, as with everywhere, more people will start their day in the morning.
