Thread:Ollerus/@comment-5275759-20200101001107/@comment-24758887-20200210190734

Kamachi Kazuma Official Website recently reclassified OT and NT into five arcs. Source
 * OT1-10: Academy City Arc
 * OT11-22: God's Right Seat Arc
 * NT1-10: Othinus Arc (formerly known as Gremlin Arc)
 * NT11-18: Magic God Arc
 * NT19-22R: Coronzon Arc

Two years ago, the official names for the different Index arcs appeared in the Dengeki PlayStation magazine.
 * OT1-10: Academy City Arc
 * OT11-22: Versus Roman Catholic Church Arc
 * NT1-10: Gremlin Arc
 * NT11-19: Fall of Academy City Arc