Hedera will be upgrading the mainnet to v0.5.8 (release notes: https://hedera.io/release-notes
) on Thursday, May 21st, at 17:00 UTC. Nodes 2 and 3 will be brought back online and node 5 (run by Hedera in GCP) will be replaced by a node run by Google. This upgrade will take approx. 120 minutes to complete, during which time all network services will be offline.