I'm going to assume this is a joke?

Just in case it isn't, I guess I should spell out just what my above statement was meant to imply:

When I said "the Imperium ignores individual planetary time," I did NOT mean that individual Imperials on an actual planet - let alone the locals themselves thereon - will necessarily ignore planetary time. I simply meant that anything officially Imperial will be time/date stamped using Imperial time, never local time. Whenever translation between Imperial and local time becomes important, there will be all sorts of automated means - such as mobile phone aps - to enable easy conversion back and forth.

Day/night cycles will be maintained by whatever means are easiest in the particular situation. If the natural situation is fairly close to Sylean-normal, then no adjustments are normally made to people's behavior. But if the divergence is enough to prevent easy acclimitization/adaptation, then humans (both local and Imperial) will live under conditions of artificial illumination that closely mimics a Sylean-normal day. In situations without a natural day/night cycle - such as on a space station or an asteroid colony - such an artificially illuminated Sylean-normal cycle will be the standard.