Hadean
The Hadean () is a geologic eon of the Earth pre-dating the Archean. It began with the formation of the Earth about 4.6 billion years ago and ended, as defined by the ICS, 4 billion years ago. , the ICS describes its status as ""informal"". Geologist Preston Cloud coined the term in 1972, originally to label the period before the earliest-known rocks on Earth. W. Brian Harland later coined an almost synonymous term, the "Priscoan period", from "priscus", the Latin word for "ancient". Other, older texts simply refer to the eon as the Pre-Archean.
Hyborian Age
The word "Hyborian" is derived from the legendary northern land of the ancient Greeks, Hyperborea, and is rendered as such in the earliest draft of Howard's essay "The Hyborian Age." Howard described the Hyborian Age taking place sometime after the sinking of Atlantis and before the beginning of recorded ancient history. Most later editors and adaptors such as L. Sprague de Camp and Roy Thomas placed the Hyborian Age around 10,000 BC. More recently, Dale Rippke proposed that the Hyborian Age should be placed further in the past, around 32,500 BC, prior to the beginning of the last glacial period. Rippke's date, however, has since been disputed by Jeffrey Shanks who argues for the more traditional placement at the end of the ice age.