I would also like to know what the "date pattern" is please. I've have this jail enabled on all servers and it hasn't been catching any bots (specifically GPTBot), and believe that may be the cause. I am using the stock conf/regex patterns.
Also, just for peace of mind... Will any changes be overwritten in future Plesk updates, or are these jails completely safe to modify?
[Edit]
The date pattern is:
datepattern = ^[^\[]*\[({DATE})
{^LN-BEG}
At the bottom of /filter.d/apache-badbots.conf