NOTE: This concept should only be applied to the single #0 issues.
After a successful first year of The New 52, in order to celebrate, DC Comics renumbered all the New 52 titles to #0 in September 2012. The initiative intended to tell new origin stories of the starring characters, or fill in gaps that were left in the five year gap between the emergence of super-heroes in the current universe, and present day. Zero Month also introduced brand new characters to the DCU, most notably Simon Baz, an Arab-American Green Lantern, created by Geoff Johns.
Despite being intended fore The New 52, there were actually 55 #0 issues, as three cancelled titles also received #0 issues, before ending. Among the cancelled titles were Resurrection Man, Voodoo, Captain Atom, and Justice League International (which was cancelled the month before, but received an annual, instead of a #0 issue).
Replacing the cancelled titles, four more books launched during Zero Month, including The Phantom Stranger, Team 7, Sword of Sorcery and Talon.