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.
Kurdish calendar
Some claim that the Kurdish calendar starts at 700 BC; this was the year Deioces united the Medes according to Herodotus. However, the claim of unification by Herodotus is proven wrong. The Medes still were vassals of the Assyrian Empire. The Median kingdom and the founding of its capital city at Ecbatana (modern Hamadan) was probably not before 625 BC when Cyaxares (grandson of Deioces) succeeded in uniting the many Median tribes into a single kingdom. In 614 BC, he captured Ashur, and in 612, in an alliance with Nebuchadnezzar of Babylon, his forces stormed Nineveh, putting an end to the Assyrian Empire.