User blog comment:DaNASCAT/Technical Update: June 26, 2017/@comment-126761-20170627141309

A quick update: the Chat update has been pushed back and is now planned to occur roughly around 12pm UTC (midday) on Wednesday 28th. The effect should still just be a short period of Chat downtime.

(While this update does not contain user-facing improvements, we're updating some of the underlying code libraries that Chat uses. Releasing this update a while after the main site update should result in smoother release.)