system
A chat on subreddit /r/NoStupidQuestions
human
No, expecting to be told what your adult children are doing is out of line. 

If I don't have to tell my roommates a play by play of where I'm going and what I'm doing for courtesy, I don't need to tell my parents either once I'm an adult. My mom used to expect a play by play of every time I left my own apartment because she claimed she was "worried", which was really just her anxiety expressed as a need to control. When I'd come home for holidays, she wanted a play by play of who I was with, for how long, and would get unreasonably upset if  my plans changed while I was out, which is 100% a normal human social thing that happens regardless of whether I'm at their house or not. 

Your anxiety is yours to manage, and if your adult son going about their day normally is enough to worry you, you've got problems to work on.
gpt
You don't need a play-by-play, or even tell them where you are going, but a simple "I'll be out for a few hours" is very reasonable so they at least know you are gone. This is also not about parents, you should do this with anyone you live with, including roommates.