The middle of the three periods which comprise the Cenozoic era, preceded by the Palaeogene and followed by the Pleistogene, beginning 23.03 Ma ago and ending 1.81 Ma ago. The Neogene period is divided into the Miocene and Pliocene epochs.
http://www.geologypage.com/2014/05/neogene-period.html Neogene Period.