I sent a email to support team of prison server cause there was no specific time servers would go live on the 21st, they replyed with this...
Hello. We expect to be opening the game servers 21 of september, between 8:00 PM
and 11:00 PM on GMT +1 TimeZone.
Anyway, we can run into some type of trouble, but we're always commited to keep
our release date. Any trouble, unless major flaw, would delay a few hours the
launch.
We'll publish a big "We're open" sign when the game it's ready to login to.