According to Ethereum’s official announcement, the hard-fork will happen on Saturday, December 7, 2019, however, users are advised to upgrade their node before today, December 1 to account for the variable block times. You can check the official countdown of the hard-fork here
Istanbul is a hard-fork which means that it will change the underlying protocol of Ethereum by creating brand new rules in the system. The official Ethereum Improvement Proposals (EIPs) are as follows:
- Align the costs of opcodes with their computational costs and improve denial-of-service attack resilience.
- Make layer 2 solutions based on SNARKs and STARKs more performant.
- Enable Ethereum and Zcash to interoperate.
- Allow contracts to introduce more creative functions.
This is one of the first real steps of the current transition from Proof of Work to Proof of Stake that Ethereum is undergoing. The hard-fork will not affect users that are holding Ethereum on exchanges or personal wallets, however, node operators and miners will need to download the latest version of the Ethereum client in order to run Istanbul. Similarly, developers with contracts on the Ethereum network will need to review all the EIPs included in the hard fork to check whether they will affect their contracts or not.