How to get teen to come home on time?

It is hard to know if this is an obedience issue or a skill set issue from what you wrote. If he just can’t keep track of time, have him set alarms on his phone. If the former, perhaps back off and give him more autonomy. After all he will be an adult in two years so should probably start practicing now. I don’t think taking privileges away is the right response. Talk to him and explain why you think it is important to you and listen to why he wants to stay out and disobey you. Are there places where you can put the decision making back in his hands? I think if you could reach a compromise where you say it is really important to you that he always be home by midnight on Friday nights but that you will let him decide what time to come home on weekdays as long as it is before 7pm (or whatever works for you) and homework gets done etc that you could show him you trust his judgment and improve your relationship and communication. If he disobeys explain how it makes you feel and why it worries you etc. frame it in terms of wanting the best for his life and happiness and tell him you know it is ultimately up to him to decide and that you know you can’t control him. I think it is pretty normal for boys that age to want to disappear away from families most of the time. 

Have there been an actual problems as a result of his not being home? If there are no problems, you need to loosen up. Instead of telling him when to be home, ask him where he is going and when he will be back. Everyone will be much happier. 

Oh, I saw some responses and I did not feel they get how annoying this can be. So I thought I'd chip in. It can be so frustrating, even during daytime hours when you're pretty sure they are safe: Where is she? What is she doing? Who is she with? When will she be home? Why isn't she answering texts/calls, etc.?  From her point of view it's just "calm down, i'm fine, I'm just hanging out with friends, you wouldn't harass my brother this way." Completely oblivious about time and the impact she is having on others. 

I'm having a bit of a breakthrough by helping her see why I want to know, and how frustrating it is to have the lack of certainty. I've shown her brother doesn't get harassed because he replies to my texts, tells me when he'll be home, and updates me (sort of) accordingly.  In response to this, she knows she needs to inform us "who what where when" when she leaves and we have a check in time.  heading out in the afternoon? Great. I'm planning on you being home at 6 for dinner. if that is not going to happen, you need to call by 5:30 and discuss it with me" . Sounds so simple but we've been locked in a battle and she didn't know why. She knows it's based on: I want to know she's safe; I need to know if she's home for dinner; I need to know if she is going to need a ride, etc. That makes more sense to her. Also, we made her turn on location services and she HAS to answer calls/texts or no phone. 

Good luck!