The Ethereum network will be undergoing a scheduled upgrade at block number 9,200,000, which is predicted to occur on Wednesday, January 1, 2020. The exact date is subject to change due to variable block times and timezones.
Please upgrade your node before Wednesday, December 30, 2019 to account for the variable block times.
Ethernodes.org has kindly provided Istanbul node statistics and a countdown timer located at https://ethernodes.org/muir_glacier. etherscan.io has provided a countdown timer located at https://etherscan.io/block/countdown/9200000. You can monitor the network upgrade in real time at http://forkmon.ethdevops.io/ (it will be updated shortly before the fork).
If you use an exchange (such as Coinbase, Kraken, or Binance), a web wallet service (such as Metamask, MyCrypto, or MyEtherWallet), a mobile wallet service (such as Coinbase Wallet, Status.im, or Trust Wallet), or a hardware wallet (such as Ledger, Trezor, or KeepKey) you do not need to do anything unless you are informed to take additional steps by your exchange or wallet service.
Download the latest version of your Ethereum client:
NOTE: Harmony (ethereumJ) is now a deprecated client and will not be supporting Istanbul. Besu is a mainnet compatible Ethereum client written in Java.
A big thanks to the Ethereum community and to all Ethereum developers across all clients and platforms who came together to provide input, thoughts, and contribution.
DISCLAIMER: This is an emergent and evolving highly technical space. If you choose to implement the recommendations in this post and continue to participate, you should make sure you understand how it impacts you. You should understand that there are risks involved including but not limited to risks like unexpected bugs. By choosing to implement these recommendations, you alone assume the risks of the consequences. This post and recommendations are not a sale of any kind and do not create any warranties of any kind including but not limited to any relating to the Ethereum network or the Ethereum clients referred to herein.