Some background:
I have a Java 1.6 webapp running on Tomcat 7. The database is MySQL 5.5. Previously, I was using Mysql JDBC driver 5.1.23 to connect to the DB. Ever
I also was having the exact same problem in LibreOffice Base. So I just specified a non 'daylight savings time zone' in the connection string.
I tried without the "&serverTimezone=MST" but that failed as well.
I also tried "&serverTimezone=MDT" and that failed, so for some reason, it doesn't like daylight savings time!