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.
Ionians
Before then, the Yavanas appear in the Vedas with reference to the Vedic period, which could be as early as the 2nd millennium BC. The Vedas are to be distinguished from the much earlier Vedic period. In the Vedas, the Yavanas are a kingdom of Mlechhas, or barbarians, to the far west, out of the line of descent of Indic culture, in the same category as the Sakas, or Skythians (who spoke Iranian), and thus probably were already Greek. The Ionians of the Aegean are the identity customarily assigned to them.