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Why Bitcoin halving calculators are out of sync
The halving of the Bitcoin network is fast approaching and, according to the latest estimates, will likely happen in seven days (April 19). But trying to pin down the exact minute or even hour for this pre-planned programmatic upgrade is surprisingly unpredictable. Take a look at any of the Bitcoin halving countdowns online – they’re all out of sync!
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Guru Observer, for example, shows that the halving will occur in seven days, seven hours and 20 minutes, while CoinMarketCap says it will occur two hours later. The “Bitcoin Block Reward Halving Countdown” states that it will happen in seven days and 15 hours. While these estimates are all generally in line, someone looking to trade the halving might get a little frustrated.
The Bitcoin halving is expected to occur every 210,000 blocks, which is approximately every four years. This particular event will be executed automatically by the network exactly at block height 840,000. Based on the way Bitcoin creator Satoshi Nakamoto designed the system, bitcoin miners “find” the next block to put into the blockchain every 10 minutes, meaning it should be easy to figure out exactly when the next one should happen halving.
In practice, however, things are a little more complicated.
“Calculating the time it takes for bitcoin to halve has three important elements: the current block height, the block where the next halving occurs, and the average block time,” according to Simon Cousaert, data director at The Block Research (which currently predicts that the halving will fall in seven days, 15 hours and 40 minutes).
“Because the second element, the target block, is a constant, the accuracy of the countdown depends on the height of the current block and the average time of the block,” he said. Likewise to count the height of the current block, which should be an easy data to retrieve.
Where the discrepancy likely comes into play is how different halving calculators count the time between blocks. Again, in theory the time it takes to mine a block should also be 10 minutes, by design. But the number of miners directing the computing power to mine and secure the Bitcoin blockchain is not static, meaning that figure can vary.
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“The average block time is more difficult to estimate accurately,” Cousaert said. “You can take a simple constant and assume that each block takes 10 minutes to mine.” But what halving calculators probably do is take “the rolling average of the block time” on some time scale, be it the last 100, 90, or 30 days (or any other arbitrary time period).
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“This does not necessarily lead to a more accurate forecast, because the average of the last few days does not necessarily predict the average of the next few days,” Cousaert added.
Marko Tarman, lead mining manager at NiceHash, echoed this point by saying that everyone in the world has the same access to some “static” data regarding Bitcoin: block height halved. However, there are two other “dynamic pieces of information”, the height of the current block and the time of the block.
“It is important to note that block times can vary considerably,” Taman said. “If average block times are less than 10 minutes, the predicted halving event will appear to occur sooner. Conversely, if average block times exceed 10 minutes, the halving event will appear to be delayed.”
In other words, the countdown to halving – an event not only known in advance, but actively anticipated to the point that people debate whether it is “priced in” – is more art than science.
“While this detail may not be critical when looking at the countdown a year in advance, precision becomes increasingly important as the event gets closer,” Tarman said.