I was about to ask the same question.
I understand that you have to wait until you have your IFR Rating until you can change time and weather.
However this does not seem to work.
I set it to realtime and weather for the mission I’m currently flying but the mission time instead gave me 22nd August at 9:15 UTC.
Temperature, Pressure and wind, seem to match real time though. Cloud coverage and time and date do not.
I don’t know whether this is by design since I’m still at the point in my career were I fly for other companies instead of my own. So maybe date and time is supposed to be fixed by the employer? And this will change as soon as I open up my own company? But I somehow doubt it.