The unit mya is an acronym and stands for engl. million years ago "Million (s) years ago ", " in front of x million (s) years." It is not to be confused with the million years. mya is mainly used in archeology and geology ( geological time scale) as a unit of measure used to specify a particular point in the past. Reference point for a time is the present, the now (for example, today or this year) passing time can be viewed as a moment.
More specifically, mya is only one - albeit the most common - use the "base unit " ya ( years ago) with a prefix. It is thus in line with the far lesser-used abbreviations tya ( thousand years ago, "A thousand years ago " ) and bya ( billion years ago, "Billion (s) years ago ").
Conflicts to the international system of units and solutions
The abbreviation mya corresponds to three points, which can be assigned one of their letters, not the International System of Units ( SI):
Is not entirely clear at times with mya whether the abbreviation is to be taken literally and they actually refers to the respective Now the viewer or whether there is an accurate reference date or exact zero. For the latter, for example, the year 1950 called (as in Before Present ), possibly also comes into question as the year zero reference point. However, since usually for periods of several million years is at times with mya, the span of approximately 2000 years, in which the three "possible" reference points mentioned here are, almost always neglected.