When did the Nazi book burning period start?

On May 15, 1933, the Main Office for Press and Propaganda of the German Student Union proclaimed a nationwide "Action against the Un-German Spirit", which was to climax in a literary purge or "cleansing" ("Säuberung") by fire. Local chapters were to supply the press with releases and commissioned articles, sponsor well-known Nazi figures to speak at public gatherings, and negotiate for radio broadcast time. On the 8th of April, the Student Union also drafted the Twelve Theses which deliberately evoked Martin Luther and the historic burning of "Un-German" books at the Wartburg festival on the 300th anniversary of the posting of Luther's Ninety-Five Theses. The theses called for a "pure" national language and culture. Placards publicized the theses, which attacked "Jewish intellectualism", asserted the need to "purify" German language and literature, and demanded that universities be centres of German nationalism. The students described the "action" as a response to a worldwide Jewish "smear campaign" against Germany and an affirmation of traditional German values.

http://en.wikipedia.org/wiki/Nazi_book_burnings

Chetak

There were probably Germans who disagreed (they were not all Nazis), but if you did that, you'd be the next to be thrown in the fire. There was a big book burning by the Nazis on May 10, 1933. This was a concerted effort throughout Germany, often by university students. There were some book burnings that did not take place that day and were postponed until June. I don't believe there was anything you could call a "book-burning period," though.