Openfire has trouble connecting to the database. The error is pretty well described by the message: it fails to properly process a time zone setting. There are a few ways to resolve this, as suggested by https://stackoverflow.com/questions/26515700/mysql-jdbc-driver-5-1-33-time-zone-issue:
Either configure your server with a timezone, or add a time-zone directive in the connection string. The first thing is something you’ll need to do on the mysql-side. The last thing you can do by modifying the string that is stored in the openfire.xml file.