During an Ethereum Core Developers Meeting on September 22, 2017, a tentative date for the Metropolis update was revealed.
In conversation, Ethereum core developers Hudson Jameson, Péter Szilágyi, Ethereum founder Vitalik Buterin, and others revealed that Byzantium upgrades will be implemented around October 17. Jameson confirmed to ETHNews that the hard fork for Byzantium is scheduled to launch on block 4,370,000, barring any major setbacks.
Initial stages of the Byzantium hard fork were tested on the Ethereum Ropsten test network as of block number 1,700,000 on September 17, 2017. Days later, the developers doubled the rewards for certain bug bounties related to the release. As developers hitherto mentioned, the increased bounty would extend until the mainnet hard fork. With a date in hand, testers have been effectively issued a deadline.