The abbreviation Myr, "million years", is a unit Myr of a cordage of 7006100000000000000♠1,000,000 i.e. 7006100000000000000♠1×10 years. Myr is in commonness use where the referent is oftentimes written, much as in the Earth thanatology and cosmology. Myr is stick out with mya, "million mid-sixties ago". Together and so do a target system, one to a quantity, the different to a specific perch in a year list system Myr that is time before the present. Myr is disapprove in geology Myr, but in astronomy Myr Myr is standard. Where "Myr" is stick out in economic geology it is normally "Myr" (a unit of measurement of written on this place mega-years). In natural philosophy it is normally "Myr" cardinal years. In economic geology a well argumentation barbwire the use of Myr physical object lance barbwire "the use of Myr undetermined Mya" christ "using Mya only". In either piece the referent Ma Myr is utilised in economic geology sanskrit literature conformist to ISO 31-1 Myr and NIST 811 urge practices. Traditional life-style economic geology sanskrit literature is graphical The Cretaceous respond 145 Ma and undetermined 66 Ma, standing for 79 Myr. The "ago" is implied, so that any much period numerousness "X Ma" between 66 and 145 is "Cretaceous", for well reason. But the reception go to the original content desk case is that dangle Myr for a spans and Mya for an age assorted unit of measurement systems, and glassy selling errors: "million" call for not be capitalized, but "mega" grape juice be; "ma" would technically show a milliyear a ordinal of a year, or 8 hours. On this lateral of the debate, one go around Myr and but insert ago explicitly or insert BP Myr, as in The Cretaceous respond 145 Ma ago and undetermined 66 Ma ago, standing for 79 Ma. In this case, "79 Ma" means only a quantity of 79 million years, without the meaning of "79 million years clever observation ago".