I have always had a curiosity about how bitcoin halving services calculate the countdown. For example, you have
NiceHash that says halving will happen on May 2 and websites
like this that have a quite different date.
Why this difference if halving happens after a fixed number of blocks?
Because the period between successfully mined Bitcoin blocks is not always the same; Therefore, it is natural that there will be differences in the predictions* of the halving times displayed by the two websites.
* You can see that at
https://www.nicehash.com/ it says 'ETA', while at
https://bitcoinhalving.info/ it says 'expected'
Because the number of bitcoins created each time a user discovers a new block - the block reward - is halved based on a fixed interval of blocks, and the time it takes on average to discover a block can vary based on
mining power and the network
difficulty, the exact time when the block reward is halved can vary as well. Consequently, the time the last Bitcoin will be created will also vary, and is subject to speculation based on assumptions.