H. P. Blavatsky

Naros. A cycle, which the Orientalists describe as consisting of 600 years. But what years? There were three kinds of Neros : the greater, the middle and the less. It is the latter cycle only which was of 600 years. (See “Neros”.).

Source: H. P. Blavatsky, The Theosophical Glossary, art. Naros