On what exact date was the Bitcoin genesis block mined?

The Bitcoin genesis block was mined on January 3, 2009.

Known as block 0, the genesis block is the starting point of Bitcoin’s blockchain. Satoshi Nakamoto mined it when the Bitcoin network came into existence, creating the first block and establishing the initial 50-bitcoin block reward. Unlike later rewards, the genesis block’s reward cannot be spent in the normal way because of how Bitcoin’s software treats that coinbase transaction.

The block also contains the famous headline message “The Times 03/Jan/2009 Chancellor on brink of second bailout for banks.” It refers to a January 3, 2009, headline in the British newspaper The Times and is commonly interpreted as both a timestamp clue and a comment on the instability of the banking system.

January 3 is often confused with October 31, 2008, when Nakamoto announced the Bitcoin white paper. January 9, 2009, is another nearby date: that was when the first open-source Bitcoin software release became available. Those milestones are distinct from the genesis block’s mining date.