The Bitcoin halving is an event that repeats itself every time when 210,000 blocks are mined. Every time that a block is mined, the miner gets rewarded with a certain amount of Bitcoin. A block gets mined or created every 10 minutes in the Bitcoin blockchain. With this, we can say that it takes approximately 4 years to have the Bitcoin halving event and get the mining rewards reduced by half.
So far, we’ve witnessed a total of 3 halving events since Bitcoin was created. Below, are the dates on which the events have happened, and the rewards per block: