# Byzantium HF Announcement

DevFeed: [Byzantium HF Announcement](<https://devfeed.tech/articles/byzantium-hf-announcement-16813.md>)

Original publisher: [Read original article](<https://blog.ethereum.org/en/2017/10/12/byzantium-hf-announcement>)

Author: Ethereum Foundation

Published: 2017-10-12T07:51:59Z

Content type: release

Language: en

Sources: [Ethereum Foundation Blog](<https://devfeed.tech/sources/ethereum-foundation-blog.md>)

Topics: [Ethereum](<https://devfeed.tech/topics/ethereum.md>), [Network](<https://devfeed.tech/topics/network.md>), [Development](<https://devfeed.tech/topics/development.md>), [client](<https://devfeed.tech/topics/client.md>)

Tags: [2017](<https://devfeed.tech/tags/2017.md>), [announcement](<https://devfeed.tech/tags/announcement.md>), [cryptographic](<https://devfeed.tech/tags/cryptographic.md>), [development](<https://devfeed.tech/tags/development.md>), [ethereum](<https://devfeed.tech/tags/ethereum.md>), [fork](<https://devfeed.tech/tags/fork.md>), [implement](<https://devfeed.tech/tags/implement.md>), [network](<https://devfeed.tech/tags/network.md>), [protocol-announcements](<https://devfeed.tech/tags/protocol-announcements.md>), [rsa](<https://devfeed.tech/tags/rsa.md>), [upgrade](<https://devfeed.tech/tags/upgrade.md>)

## AI overview

Ethereum announced a planned Byzantium hard fork at block 4,370,000, expected between 12:00 and 13:00 UTC on October 16, 2017. The announcement lists client versions and protocol changes, including new opcodes, transaction receipt status fields, cryptographic operations, a delayed difficulty bomb, and a reduced block reward.

## Source excerpt

The Ethereum network will be undergoing a planned hard fork at block number 4.37mil (4,370,000), which will likely occur between 12:00 UTC and 13:00 UTC on Monday, October 16, 2017. The Ropsten test network underwent a hard fork on September 19th (UTC) at block number 1.7mil (1,700,000). A countdown timer can be...