bya
bya or b.y.a. is an
billion years ago". It is commonly used as a unit of time to denote length of time before the present in 109 years. This initialism is often used in the sciences of astronomy, geology, and paleontology
.
The "billion" in bya is the 109 "billion" of the
Ga (Giga-annum), however, bya remains in more widespread use.[1] In 1974, the UK switched from the long scale to the short scale.[1]
Related units are
Ga or Gya has a capitalized
first letter instead.
See also
References