It seems that recent Ubuntu or MySQL update changed something about the timezones. Here a user fixed similar issue by editing the mysql config file (you should put a time zone that is correct for you) Openfire doesn't start in linux. May be a timezone problem?
You can also edit the /conf/openfire.xml and edit the database connection string as described here https://stackoverflow.com/questions/26515700/mysql-jdbc-driver-5-1-33-time-zone-issue: