Rust had been stewing around in Graydon's head for years, but he was never paid to work on it until 2009 (part-time, at that point). And he didn't have any paid employees to help him until 2010 (that would be pcwalton). And as far as I'm concerned, Rust development didn't actually start in earnest until mid-to-late 2011, when the compiler began bootstrapping. And the Rust that we know and love today didn't begin to take shape until 2012, when borrowed references started taking shape.

Personally, I consider the 0.1 release in January 2012 to mark Rust's "birthday". Everything prior to that was just gestation. :)