In 1991–1994, Iran combined all of these laws into the unified "Islamic Penal Code" which consisted of five "Books".[14] The new Islamic Penal Code was adopted in January 2012 and incorporates the bulk of penal laws in the IRI, replacing Books One through Four of the old code.[15] Book Five of the Islamic Penal Code ("the only part of the Penal Code that has been adopted permanently and is not subject to experimental periods") passed on May 22, 1996.[16]