The Bitcoin project was registered on November 9th, 2008. The Bitcoin network started up on January 3rd, 2009 with the genesis block. The genesis block contains a media reference to the dealings of a central banker in the UK.
Bitcoin can trace its origin to the B-money Proposal. The paper Bitcoin: A Peer-to-Peer Electronic Cash System describes the early concepts behind Bitcoin and and precedes the first release of Bitcoin software.