The homepage, forum, wiki and IRC will be going offline for about five minutes on 2018-04-29, between 09:00 and 09:15 UTC.
For convenience, this means:
EDT (USA east coast):
2018-04-29, 05:00-05:15
BST (UK):
2018-04-29, 10:00-10:15
CEST (Most of Europe):
2018-04-29, 11:00-11:15
AEST (Australia east coast):
2018-04-29, 19:00-19:15
The intent is to install security updates on the server which hosts the homepage, forum, wiki and IRC. These will be non-disruptive to functionality, as the server is running a stable OS release that gets critical fixes only.