The first block has a special status
The genesis block is block height zero, whose parameters Bitcoin software knows in advance. It has no preceding block and provides the common starting point to which every valid chain leads. Its timestamp corresponds to 3 January 2009 and its coinbase transaction specifies a reward of 50 BTC.
Bitcoin Core also notes that this particular reward output cannot be spent because it was not originally inserted into the database in the ordinary way. That is a technical peculiarity of the genesis block, not a general rule for later block rewards. Other valid rewards can be spent after their maturity period.
The newspaper headline is evidence and symbol
The block contains the text The Times 03/Jan/2009 Chancellor on brink of second bailout for banks. Referring to that newspaper headline demonstrates that the block could not have been made before the story was published. It is a simple time anchor independent of the author's assertion.
The headline also links the launch to the banking crisis and is widely read as criticism of bailouts. That is a strong interpretation, but it should still be labelled interpretation. A string of bytes cannot reveal the anonymous author's complete political philosophy.
The first public version was open and experimental
On 8 January 2009 Satoshi announced Bitcoin v0.1. The program ran on Windows and included open C++ source code. Once started, it could connect automatically to other nodes. The author asked people to keep nodes accepting incoming connections because doing so would help the tiny network.
The announcement explicitly described the software as alpha and experimental. Initial difficulty was extremely low so that an ordinary computer could find a block. There was no public token sale or corporate allocation, but only a small technical community saw the launch and Satoshi was unquestionably among the earliest miners.
- 3 January 2009: the genesis block's timestamp
- 8 January 2009: public announcement of Bitcoin v0.1
- open source code and the ability to run one's own node
- a small experimental network, not an instantly global monetary system
Decentralisation is a process property, not a date
At launch one author knew the code and network best, and participation was small. Calling day one perfectly decentralised would be inaccurate. The design did allow others to inspect, copy, run and later develop the program without requesting shares in a company or a licence to use the network.
Nodes, mining, development and coin ownership became more distributed over time. That distribution is not guaranteed forever, and concentration can reappear in every area. What matters is that users can verify consensus rules and reject blocks or software that violate them.