 It is currently estimated to span the time between 2.580 ± 0.005 Ma (million years ago) and 0.773 ± 0.005 Ma.The term Early Pleistocene applies to both the Gelasian Age (to 1.800 ± 0.005 Ma) and the Calabrian Age.While the Gelasian and the Calabrian have officially been defined by the International Union of Geological Sciences (IUGS) to effectively constitute the Early Pleistocene, the succeeding Chibanian and Tarantian ages have yet to be ratified.