The main game clock is as Arry said fixed and displays the game time which is UTC (GMT) and the same for all of us.
For reasons that make sense to FDev a while ago they added a time stamp to the messages that display in your comms panel that time is your local time.
FD said that the comms panel time was a bug, which (I think) was fixed in 2.4.
I just mentally subtract a few hours from the displayed time; the actual number varies, depending on daylight savings time. If that's too much effort, put a clock, phone, or watch near your system.
The reason that the local time is not shown is because you really need game-time for in-game meetings. Back when I was doing the Distant Worlds Exploration, the ship clock had not yet been implemented and I missed several rendezvous because I didn't get the timing right.
The current clock is a big quality-of-life improvement, but I would still like to see a second "local time" clock in-game.