Myr

megayear

Timeexact by definition

The megayear is one million years, written Myr. It is the everyday unit of geology and evolutionary biology: a species persists for a few Myr, an ocean basin opens over tens of Myr, and a mountain range rises over roughly a hundred.

Watch out: Geologists distinguish Myr, a duration, from Ma, an age before present. Sixty-six Ma is when the Cretaceous ended; sixty-six Myr is how long something lasted. The distinction is enforced in the literature and worth respecting.

1 Myr 31,557,600,000,000 s