Keeping track of time in a meaningful way when your polity controls a dozen worlds and has trade relations with at least 5 dozen more is hard. Thus was invented the Standard Galactic Time Unit. With that system, interplanetary (and interstellar) activities have a common neutral time system to synchronise things such has Faster than Light Communication, while planet-side affairs typically use a mix of the expressing an absolute unit in the largest SGTU subunit that’ll fit in a local day, to which is added a SGTU duration after the local normalised sunrise.
For example Earth’s 30 September 2065, 13:12 UTC would be 3D13.65/1 (or 18F.3D13.6556.6AD9 for full specificity) in interstelar communication, but would be refered to as something like 3D13.6/1L+1b1af/1 "on the day that starts on 3D13.6/1 according to the Local standardised day, at 1b1af/1 past local standardised midnight.
Note however that, as of 2376, Earth, despite being a signatory of the GTCO still seldom use SGTUs in planetary affairs, oft chosing to use it’s legacy base 60 time system