|(c) 2013 Andrew Alden, licensed to About.com, Inc. (fair use policy). Data from Geologic Time Scale of 2013.
This geologic time scale represents the working edge of historical geology, showing the latest names and dates of the smallest divisions of geologic time that are universally recognized. The Mesozoic Era is the second part of the Phanerozoic Eon. For anyone but specialists, the rounded-off dates in the Phanerozoic table are sufficient. Each of these dates also has a specified uncertainty, which you can look up at the source.
The Cretaceous is a curious period. At 80 million years, it is far longer than any other Phanerozoic period, yet it has only two main subdivisions. For that reason, the 12 ages of the Cretaceous are more often used, and more widely known, than any other names of agesespecially among dinosaur enthusiasts.
The dates shown on this geologic time scale were specified by the International Commission on Stratigraphy in 2013 and the colors were specified by the Committee for the World Geologic Map in 2009.