Basil Bourque, I would not introduce another mnemonic. Fix the one which is wrong. If you still have the need to omit the T for humans, Logback should introduce

%date{ISO8601NoT} or %date{ISO8601Human}
This message is automatically generated by JIRA.
If you think it was sent incorrectly, please contact your JIRA administrators
For more information on JIRA, see: http://www.atlassian.com/software/jira