What's the right age to let your kids start dating?

Do you think if I tell you 18 is the right age or 15, then all kids would follow it? And as parents I think we can only guide our children and not dictate terms. They are not going to be open about they are dating or not. So, it is better that we give enough time and the same time space to our kids so neither they are suffocated by our opinions in their life, nor they are deprived of the right advice and guidance. Cheers!