Out of curiosity, what's your age? Have you ever gotten in trouble or have done anything like that for your parents to lose trust in you?
Odds are your parents are acting like this because they don't trust you. That's also why they don't give a reason, A parent would never want to tell their child that they don't trust them.
Basically you just have to build trust with them. It will be very helpful in many areas of your life to have a good trusting relationship with your parents. Some places to start is respecting your parents and not flipping out on them, show ur emotions constructively. When you tell them you are going to do something sometime, make sure u do it. Start trying to be your parent's friend almost, make conversation out of nowhere with them about their day and their lives, don't ignore them, treat them like people (u can even practice convo skills on them) beacuse believe it or not they are. Your parents can be some of your best friends u can have if you give them the chance, you mean more to your parents then you mean to your friends so just think about it.. After you get a healthy relationship with your parents odds are they won't be dictators.
The other possiblity is they are worried about your welfare in which case you just have to convince them you'll be safe. Just let them know where you are going and all that stuff they'd normally ask. Make sure to let your mom know after when u get home about your night. If you don't say anything about it she could wonder what you're up to.
So try to improve your relationship with your parents, that's what I've done. I've noticed a HUGE difference, everyone always says my parents are the bomb and stuff because they give me so much freedom, I never have to call them (I call them on my own freewill now and then just to let them know what's up), I don't have to say where I'm going or when I'll be back (I might say just to reassure them or something) and I can show up at the house anytime I want. I accomplished all this by getting a healthier relationship with my parents, it isn't that hard of a thing to do beucase odds are your parents have been waiting for you to soften up for a long time.