Neoproterozoic Era. This was the last era of the Proterozoic, and lasted from about 1.0 billion to 542 million years ago.
This era and its periods are all dated chronometrically rather than stratigraphically, except for the very last part (the Ediacaran), which has been defined bio-stratigraphically. Stratigraphic labels depend upon the establishment of Global Boundary Stratotype Sections and Points (GSSP's), which are globally prevalent markers in the strata that distinguish one period from another. The stratigraphy of the Precambrian is not well established, but it is a work in progress and new developments continue to be made. A list of currently accepted GSSP's for different ages of the Earth's history can be found here.
Cryogenian Period: 850–630 mya. Ediacaran Period: 630–542 mya.