Halving day 2012 (November 28, 2012) was the day of the first subsidy halving, which occurred when block 210000 was solved. Until ?block 420000, the block reward would be 25 BTC instead of the original 50 BTC.

At the moment before the halving, 10,500,000 BTC had been mined, 50% of the target cap.

Solution

Block 210000 was found and broadcast on 2012-11-28 at 15:24:38 UTC. (2.1) ?Slushs pool was responsible for finding the solution, (2.2) and a miner named laughingbear contributed the solution. (2.3)

The block was solved by a Radeon HD 5800 (2.4) after mining for less than a week. (2.5) This GPU would later be sold to ?Chaang Noi at a significant markup on August 26, 2013. (2.6) Several images of the card were posted to ?Bitmit, but no copies are currently known to exist. (2.7)

References

2.1: Day: 28 Hash: 000000000000048b95347e83192f69cf0366076336c639f9b7228e9ba171342e Month: 11 Year: 2012
2.2: 28 November 2012 Id: 128200
2.3: 27 November 2010 Id: 1976
2.4: 28 November 2012 Id: 128200 Post: 1364739
2.5: 28 November 2012 Id: 128221
2.6: 5 April 2013 Id: 168342
2.7: 29 July 2015 Id: 1138466