History Ireland is a magazine with a focus on the history of Ireland rather than archaeology. The first issue of the magazine appeared in Spring 1993. It went full-colour in 2004 and since 2005 it is published  bi-monthly. It features articles by a range of writers and book reviews. The magazine's editor is Tommy Graham of the Tisch School of the Arts, New York University, Dublin Programme. In 2017, the magazine attracted significant online criticism for publishing an allegedly defamatory letter about historian Liam Hogan and his work on the Irish slave myth. In September 2017, the magazine's editor issued a formal apology to Hogan.
Question: How many years has History Ireland been published bi-monthly?
Answer: 13