While starting a new space program, the splash screen tells you it's December 2, 1971, yet the game clock is set to the current system date/time, and as a coincidence, it usually makes for me the mission happening in the middle of the Mars night, unless I adjust the system clock before starting the game.

I suggest setting the time of beginning of the Mars 3 intro mission to fixed: December 2, 1971, 13:52:10 UTC (or something around), and then reset it back to the system time after finishing Mars 3 / Prop-M tasks, when the next splash screen appears.