Cryptic (geology)
The Cryptic era is an informal term for the earliest geologic evolution of the Earth and Moon. It is the oldest (informal) era of the Hadean eon, and it is commonly accepted to have begun close to 4533 million (about 4.533 billion) years ago when the Earth and Moon formed. No samples exist to date the transition between the Cryptic era and the following Basin Groups era for the Moon (see also Pre-Nectarian), though sometimes it is stated that this era ended 4150 million years ago for one or both of these bodies. Neither this time period, nor any other Hadean subdivision, has been officially recognized by the International Commission on Stratigraphy.
Timeline of Arda
The Years of the Sun begin with the Awakening of Men in about V.Y. 5000. 
From this time, the First Age lasts for another 590 years.
The Second Age extends to 3441 years, beginning with the foundation of Mithlond (the Grey Havens) under Círdan, and Lindon as the Noldorin Kingdom under Gil-galad, and ending with the defeat of Sauron at the hands of the Last Alliance of Elves and Men.
The Third Age extends to 3021 years, ending with the final defeat of Sauron in the War of the Ring and the establishment of the Reunited Kingdom of Arnor and Gondor.
The Fourth Age is mainly outside the scope of Tolkien's legendarium, beginning the suggested transition to the historical period, but Tolkien gives a summary of the first two centuries of the Fourth Age.