Given the task definition and input, reply with output. This task is about reading the given passage and construct a question about the information present in the passage. Construct a question in such a way that (i) it is unambiguous, (ii) it is answerable from the passage, (iii) its answer is unique (iv) its answer is a continuous text span from the paragraph. Avoid creating questions that (i) can be answered correctly without actually understanding the paragraph and (ii) uses same words or phrases given in the passage.

For the past 25 years, the Tucson Folk Festival has taken place the first Saturday and Sunday of May in downtown Tucson's El Presidio Park. In addition to nationally known headline acts each evening, the Festival highlights over 100 local and regional musicians on five stages is one of the largest free festivals in the country. All stages are within easy walking distance. Organized by the Tucson Kitchen Musicians Association, volunteers make this festival possible. KXCI 91.3-FM, Arizona's only community radio station, is a major partner, broadcasting from the Plaza Stage throughout the weekend. In addition, there are numerous workshops, events for children, sing-alongs, and a popular singer/songwriter contest. Musicians typically play 30-minute sets, supported by professional audio staff volunteers. A variety of food and crafts are available at the festival, as well as local micro-brews. All proceeds from sales go to fund future festivals.
When is the Tucson Folk Festival held?