What have been the dates of past Bitcoin halving and when precisely is the next one expected to happen?
No one actually knows, but it is possible to calculate an estimate of when it might happen.
The only thing certain is that it will happen at block 840,000, but no one knows precisely when this block will be mined.
What the Bitcoin protocol dictates and why halving dates are important
No date is specified in the Bitcoin protocol.
The protocol dictates only two things. The first is that the difficulty is changed every 2,016 mined blocks so that the block-time is kept as close to 10 minutes as possible. The second is that there is a halving every 210,000 blocks.
Seeing as how it more or less takes an average of 10 minutes to mine a block, mining 2,016 blocks takes about two weeks, while mining 210,000 blocks takes just under 4 years.
The actual timelines
However, the actual timelines are a bit different, because Bitcoin’s hashrate grows faster than the difficulty adjustment manages to keep the block-time close to 10 minutes.
Put another way, the average block-time (that is, the time that passes on average between the mining of one block and the mining of the next) is often less than 10 minutes.
For example, in 2022 instead of the classic 144 blocks per day, an average of about 156 blocks per day were mined, with an average block-time of just over 9 minutes.
This makes the actual timings lower than the theoretical ones.
Indeed, so far on average, it has taken only three years and just under ten months to reach a new halving.
The dates of past Bitcoin halvings
In theory, a halving should occur about every 1,458 days, or every three years and 362 days.
However, if we take the dates of the past three halvings, we find that less than 1,458 days have always passed between one halving and the next.
The first block of Bitcoin’s blockchain was mined on 3 January 2009, while the first halving occurred on 28 November 2012 at block 210,000. In total, only 1,425 days had passed, or less than three years and 11 months.
The second halving occurred on 9 July 2016 at block 420,000, which is actually only 1,319 days after the first halving. So the period had shortened to just over three and a half years.
The third and last halving occurred on 11 May 2020 at block 630,000. Since the previous one, 1,402 days had elapsed, or just over three years and ten months.
On average, therefore, a halving has occurred every 1,382 days to date, or just under three years and ten months.
Estimating the date of the next halving
In the event that the next halving were to occur 1,382 days after 11 May 2020, it would occur on 22 February 2024, but in reality the block-time in recent years has increased slightly.
In fact, at the theoretical rate of 10 minutes per block it is estimated that the date of Bitcoin’s next halving could be 1 May 1, 2024. If that were the case, 1,451 days would have elapsed since the previous halving, which is the longest period ever, not far from the theoretical 1,458 days.
However, as we have seen, in reality the actual average block-time is less than 10 minutes, so this estimate could be approximated by excess.
Assuming that the actual block-time over the next two years remains similar to that of 2022 (about 9.2 minutes), it would take only 509 days from today before the 840,000 block-time that would trigger the fourth halving would be undermined. So one could estimate a date close to 17 March 2024.
Therefore, three different estimates can be made.
The first, more conservative, is that the next halving could occur on 1 May 2024 in case the average block-time from now on equals the theoretical 10-minute block-time.
The second, more optimistic, is that it will occur 1,382 days after the previous one, that is, on 22 February of the same year.
The third, more realistic, is that it will occur in 509 days, at the current rate of about one mined block every 9.2 minutes, or around mid-March also in 2024.
Past estimates and dates of the Bitcoin halvings
It is worth noting that these estimates were also made in the past for the previous three halvings, and in no case were they accurate. Obviously, the closer we get to the block that triggers the halving, the more precise the estimates become, but almost two years later, it is highly unlikely that the current estimates are accurate.
For example, the first estimate predicted that the first halving should occur in January 2013, or at most December 2012, and instead it occurred in late November 2012.
The second one actually predicted halving in November or October 2016, or at most September of the same year. Instead, it took place in July, several months ahead of the expected date.
The third estimate, on the other hand, was more accurate, because using data from the previous two halving events, the third was expected to occur in April 2020, and instead it happened in the first half of May.
The speed of mining
One very curious thing is the comparison between the average block-time in 2022 and 2021.
This is because during bull runs miners earn more money, so they can invest more to increase their hashrate. This should result in an acceleration of the speed at which blocks are mined, and thus a reduction in block-time.
Indeed, in 2021 the average block-time was 9.9 minutes, which is less than the theoretical 10 minutes.
However, in 2022, at the height of the bear market, the hashrate increased again to new all-time highs, bringing the average block-time to 9.2 minutes.
The reason is that the growth of hashrate is very slow, so it follows the growth of Bitcoin’s price several months apart. In other words, the incredible growth of hashrate during the bear market is a very late consequence of the 2021 bull run itself.
A realistic estimate
Based on this, it is possible to assume that during 2023 and 2024 the block-time may increase, and return closer to the theoretical 10 minutes. Thus a more realistic estimate of the date of Bitcoin’s next halving is between mid-March and early May 2024, or around the first decade of April.