What year was Cortana created?

It is unknown what year she was created but it is estimated that she was created circa 2550s

Cortana Quotes from halo 3

I absolutely believe you in the fact that cortana said chief leave me. She is probably delarious. In the halo 3 announcement trailer, you could even hear her scream right before her first appearence...--Halo3

Apparently the answer is too obvious, Eric Nylund's ''Fall of reach probably answer the question

When did Cortana say "leave me"?. She said something more like this: MC" Dont worry I'll get you" Cortana "Dont make a girl a promise you cant keep" --Will 16:07, 6 January 2007 (UTC)