Bitcoin’s four completed subsidy halvings began at blocks 210000, 420000, 630000, and 840000. In UTC, those blocks were mined on November 28, 2012; July 9, 2016; May 11, 2020; and April 20, 2024. The dates describe history, while the block heights define the rule. Each boundary reduced the permitted subsidy from 50 to 25, then 12.5, 6.25, and 3.125 BTC per valid block. A future halving date can only be estimated until its block arrives.
Read a halving as a block boundary
Bitcoin software determines the subsidy from block height. The first era covered blocks before 210000 at 50 BTC per block. Block 210000 began the 25 BTC era; block 420000 began 12.5; block 630000 began 6.25; and block 840000 began 3.125.
The Bitcoin developer block-chain reference explains that the subsidy started at 50 BTC and halves every 210,000 blocks. It also distinguishes the subsidy from transaction fees: together they form the block reward that a coinbase transaction may claim.
Bit.Fan’s explanation of when a Bitcoin halving happens provides the broader block-height method. A countdown shown there or elsewhere should be read as an estimate, while a completed boundary can be checked in the chain.
Put the four blocks on one timeline
Block 210000 was mined on November 28, 2012 UTC and reduced the subsidy from 50 to 25 BTC. Block 420000 followed on July 9, 2016 and reduced it to 12.5 BTC. Block 630000 arrived on May 11, 2020 and began the 6.25 BTC era.
Block 840000 was mined at 00:09:27 UTC on April 20, 2024. Its subsidy was 3.125 BTC. The explorer record for block 840000 shows the height, time, miner attribution, transactions, subsidy, and fees for that block.
Readers in the Americas may see April 19 attached to the fourth halving because it occurred during the evening in those local time zones. That is not a disagreement about the block. Use UTC when building one consistent global table and state the time zone.
Do not confuse subsidy with total miner revenue
The halving cuts newly issued Bitcoin per block. It does not divide transaction fees by two. A miner’s coinbase transaction can collect the allowed subsidy plus fees from included transactions, so the total reward for a particular block may be higher than the subsidy.
Block 840000 is an unusually clear example. Its explorer page records 3.125 BTC of newly issued subsidy and much larger transaction fees for that block. That exceptional fee result should not be treated as a normal post-halving income level. Fees vary from block to block with transaction demand and selection.
When comparing eras, label three values separately: permitted subsidy, fees in the selected block, and total coinbase output. A table headed only “mining reward” can hide which value changed by protocol and which changed with the fee market.
Verify the boundary rather than a commemorative date
To audit a historical halving, search the boundary height and the block immediately before it. Inspect the coinbase outputs and remember that pool payout arrangements may make the visible outputs more complex than a single payment. The permitted new issuance changes at the boundary even if fees obscure the total.
For example, compare blocks 839999 and 840000. The first belongs to the 6.25 BTC subsidy era and the second to the 3.125 BTC era. Comparing calendar days instead would mix many blocks from before and after the event.
Block header times are part of the block data, but they are not an external clock that proves the exact moment a miner found a solution. They operate under protocol rules and can differ modestly from observation time. For a historical guide, the height is the definitive trigger and the recorded UTC time is the practical date reference.
Estimate the next event from remaining blocks
The next boundary after 840000 is block 1050000. To make a rough estimate, subtract the current height from 1050000 and multiply the remaining blocks by an assumed average interval. At ten minutes per block, 10,000 remaining blocks suggest about 100,000 minutes, or roughly 69.4 days.
That calculation is hypothetical, not a scheduled appointment. Blocks arrive irregularly, and the recent average can differ from ten minutes. Difficulty adjustments influence the system over time but do not force each individual block to appear exactly on a ten-minute mark.
A useful tracker therefore displays current height, target height, remaining blocks, assumed interval, estimated UTC window, and last update. If the forecast changes while the target stays 1050000, the rule did not move; the observed pace did.
Keep market claims separate from issuance facts
A completed halving proves that the subsidy changed. It does not prove that Bitcoin’s market price must rise, that miner revenue must fall by exactly half, or that every miner will respond in the same way. Price, fees, hash rate, difficulty, energy contracts, and equipment efficiency are separate variables.
The durable historical record is concise: heights 210000, 420000, 630000, and 840000; UTC dates in 2012, 2016, 2020, and 2024; and subsidies of 25, 12.5, 6.25, and 3.125 BTC beginning at those blocks. Use block height for the rule and a dated explorer observation for context.