Are all 18 yo's like this?

That.

My mother instilled in my the idea that the people you are living with have a right to know where you are. When you are married, you expect to know what your spouse is up to, a general idea anyway. It's not about control. It's about respect for others and their time and care.

You can talk to him and tell him it's not about him still being "the child" but about members in a household knowing each others' schedule so they can plan and know what to expect. You can model this behavior by letting him know where you'll be (general idea anyway) and approximately how long you'll be gone. My family discusses our schedule for the week around the dinner table on Sunday evenings. It works for us. If you are sharing with him, it will make him be more willing to share with you. he'll see it as a matter of equals communicating instead of his mom still trying to keep tabs on him.

I'm pretty sure my mom knew my schedule and I had to let her know if I wasn't coming home at all. I worked mostly through dinner so that wasn't an issue.

This is what we did. With my oldest, it was hit or miss though. He was 18 and still in high school (late birthday) and felt like he should have all the freedom of 18 without the responsibility of 18. He felt like any inquiry into his whereabouts or what he had been up to was an invasion of his privacy...even if this questions were simply asked as part of random conversation. It drove me insane. No explaining to him that as members of a household it was just a matter of respect to give a brief 'hey, I am...will be back at...' 

The younger son was doing the same thing. But recently he has started coming around. A couple of weeks ago I ran up to the grocery store and told him I would be back in about 30 minutes. It was one of those times when every aisle had a friend to chat with, the lines were long and the whole trip took twice as long as it normally would. Funny kid texted me at about 45 minutes to check and make sure I was okay.

Long and short of it is that I don't think it is every kid, but there are some that take the whole turning 18, I am now an adult and don't have to answer to anyone about anything way more seriously than others.

I see that often with 18 year olds. They want to think they're grown and above having to account for themselves. With my own child and my students I simply tell them that I can treat them like complete adults if they want me to. But that would mean I was totally hands-off. Pay everything on your own, including doctors ' visits. No reminders about missing work and unexcused absences equal zeros for missed work.

It typically works for several weeks before a reminder has to be issued.

 All 18 year old aren't like that. I think your DS is being rude.

I want to say he is being rude and 'thought'less but it may very well be that he simply doesn't think about the reasoning of why you ask. Maybe a little discussion is needed. I have 4 kids and they learned early on that I wasn't simply being nosy just concerned so if they didn't appear at home in a reasonable time i might send out alerts. I do this with my husband - if I am going out somewhere I give him a general heads up as does he, now. We had a reminder talk a few months ago when he began behaving more like your 18yo. Its funny because if he comes home from work and we are all out he will call me to see where I am or if I am ok. I have received a check in call when I have been gone longer than usual at the grocery store. If my family wants dinner then I need to know when they might be home. I don't need nor ask for details about what they are doing. My older son who is back living at home is generally very good about this, even better than the youngest child. She isn't defensive about my asking, she is simply a scatter brain who might lose her head if it weren't attached.

I also sen to recall hearing my daughter's friend stalking about how when they turned 18 that their parents couldn't tell them what to do anymore. Thankfully that didn't become an issue with my daughter but it does seem to be a coming of age maturity thing for some.

We have used the word courtesy when discussing the check in policy because ultimately that is what it is. I would start there and gently remind him that there are rules in every household no matter the age because you care.

I would probably say "If you want to tell me on the days you will be here for dinner I'll plan the meal accordingly. Or you can fix what you want when you get home".

I just think it's all about trying to establish himself as an independent adult - to show you he's all grown up now and can do what he likes    Bless him 

With my girls I just made it clear that I wasn't going to be cooking meals that might get wasted and I didn't want to be worrying unnecessarily about where they were so I needed the basic information at least. They were pretty good about it.

My DD seems to think asking where she's going with MY car is treating her like a criminal. Lol. She's a good kid, tiny bit lazy but a good kid, no trouble. But, she is chafing with the 'courtesy' of following our rules with our car and in our home. I guess the newly adult thing has gone to her head

We had a talk about how being 18 entitles you to absolutely nothing. If you want a vehicle to use without strings go buy one. If you want to come and go as you please get your own place. Etc. She seemed to think 18 was a magic number and all the house rules no longer applied. Lol

I told mine that I don't have to know where she's going but it is nothing short of common courtesy to let the people you live with know when you'll be home, otherwise we worry.

So, she keeps me informed of her general movements and I don't freak the crap out on her and call out a search party. Win/win.

Mine thought that when she graduated high school. @@

My father wanted to give my daughter a used car. We said thanks, but no thanks. Because we knew her too well. If it was going to be HER car, she was going to have to be completely responsible for it. New tires, repairs, insurance, the works. If I was forking over that money, I was going to have control. 

She once thought that my threats were idle and that she could do damn well what she pleased. Her friends all lived in dorms, even though they attended the local school, and they had complete freedom. She figured she should too. She didn't like the curfew we set and broke it a few times. I had warned her but she didn't listen. So one night when she came home I told her to hand over the keys. She lost the use of the car. Told her to spend the next hour or so figuring out the bus system. Her butt was up a 6:30 to walk to the bus. Took her two hours of riding and exchanges to get six miles down the road. She made it to class on time. And learned a valuable lesson. Once she got the car back she never missed curfew again.