Paulo Coelho does not mention what time period it takes place in. Anyways, when I read the book I imagine it to be happening in the end of the 1980’s. The story is quite contemporary though.
Why do I think the story is contemporary? Let me copy a small part of an interview with Paulo Coelho. He describes the main thought of the book. After you have read that, you all will agree with the story being contemporary.
“What is the central idea in Eleven Minutes?”
“We live in a world of standardised behaviour, standardised beauty, quality, intelligence, efficiency. We believe there is a standard for everything, and we believe, too, that if we stick to that standard we’ll be safe. Because of this, we have created a kind of ‘standardised sex’, which, in fact, consists of nothing but a string of lies: vaginal orgasm, virility above all else, that it's better to pretend than to disappoint your partner, etc. As a direct consequence of this, millions of people have been left feeling frustrated, unhappy and guilty. It also lies at the root of all kinds of aberrant behaviour, for example, paedophilia, incest and rape. Why do we behave in this way with something that is so important?”
/the text above was copied from http://www.harpercollins.com/author/microsite/readingguide.aspx?authorID=1858&isbn13=9780060589271&displayType=bookinterview/ /
The theme of the book – sex and prostitution - is just a metaphor for people’s prejudices, standards and daily routine. The people look at you badly and don’t forget to judge you every single day if you differ a bit. Inside of them they dream about being different too, but they would never ever admit it. This is exactly the way it works in today’s society, therefore the book relates a lot to today’s world.