Halving

Definition
The Bitcoin halving is also known as a block reward halving, referring to the mechanism that the block reward miners receive, which decreases by half about every four years.
Bitcoin was born in 2009; the coins were issued by the process of block mining and rewards. In the beginning, each block came with 50 BTC as a reward. According to the Bitcoin protocol, with every 210,000 blocks mined, the block reward will be halved. The max supply of Bitcoin is 210,000 BTC. Currently, in the Bitcoin network, a block is generated about every 10 minutes. Hence, it is estimated that the block reward will be decreased to 0 BTC in the year 2140.
So far, Bitcoin has had three halving in November 2012, July 2016 and May 2020 respectively. The four upcoming halving is estimated in May 2024. By that time, the reward will decreases from 6.25 to 3.125 BTC.

Why the Bitcoin reward halves?
According to the law of supply and demand, if the supply of a certain product exceeds its demand, inflation will occur and the price of that product will drop severely. Similarly, Bitcoin’s value will decrease if there is a surplus.
To avoid such circumstances, the halving mechanism is designed to decrease the inflation rate of Bitcoin. This is also one of the most unique characteristics of Bitcoin compared to traditional fiat money.

Bitcoin Halving History
1. On October 31st, 2008, Nakamoto Satoshi released a paper titled “Bitcoin: A Peer-to-Peer Electronic Cash ,” introducing the concept of Bitcoin.
2. In 2009, Nakamoto Satoshi mined the first 50 BTC. At the time, the block reward of Bitcoin was 50 BTC per block. According to the Bitcoin network protocol, the block reward will decrease by half every 210,000 blocks, the max supply of Bitcoin is 21,000,000 BTC, and it is estimated that the block reward will decrease to 0 in 2140.
3. On November 28th, 2012, the first halving occurred. The block reward decreased from 50 BTC to 25 BTC
4. On July 9th, 2016, the second halving occurred. The block reward decreased from 25 BTC to 12.5 BTC.
5.On May 12, 2020, the third halving occurred. The block reward decreased from 12.5BTC to 6.25 BTC.

Halving Schedule for Other Cryptocurrencies in 2020
BEAM: On January 4, 2020, the first halving occurred. At this time, the block reward decreased from 100 BEAM to 50 BEAM.
ETC:On March 17, 2020, the first halving occurred(20% reduction, non-halving).At this time, the block reward decreased from 4ETC to 3.2ETC.
BCH：On April 8, 2020, the first halving occurred. At this time, the block reward decreased from 12.5BCH to 6.25BCH.
BSV：On April 10, 2020, the first halving occurred. At this time, the block reward decreased from 12.5BSV to 6.25BSV.
Sero(sero)：On April 14, 2020, the first halving occurred (the current block mining rewards are indefinite). At this time, the highest block reward decreased from 35.6SERO to 17.8SERO.
DASH: The estimated halving time is May 2020. It is the first halving of DASH (the block reward will decrease by 7.14%). The current block reward is 3.6 DASH.
XZC (Zcoin): The estimated halving time is September 2020. It is the first halving of XZC. The current block reward is 12.5 XZC.
ZEC (Zcash): The estimated halving time is October 2020. It is the first halving of ZEC. The current block reward is 12.5 ZEC.
ZEN (Horizen): The estimated halving time is November 2020. It is the first halving of ZEN. The current block reward is 12.5 ZEN.