]> SWEET Ontology 1 12 1 5 1 2 1 3 6 1 2 10 Epochs are divided into ages [millions of years] [Wikipedia] Periods are divided into epochs [tens of millions of years] [Wikipedia] Eras are divided into periods. [Wikipedia] Eons are divided into eras [several hundred million years] [Wikipedia] Supereons are divided into eons. [billions of years] [Wikipedia] The largest defined unit of time is the supereon, composed of eons.] [Wikipedia] The subdivisions of geologic time. The table of geologic time spans are dates and nomenclature defined by the International Commission on Stratigraphy. [Wikipedia]