I\'ve run into an interesting challenge using a PostgreSQL database with the PostgreSQL JDBC driver. It seems that the latest version of the driver, 9.2, uses the client
Just in case others struggle with this - you can edit the "conf" file that launches SQLDeveloper and add the following line :
AddVMOption -Duser.timezone=UTC
I found this file on my machine at :
/opt/sqldeveloper/ide/bin/ide.conf
Thanks to @a_horse_with_no_name for pointing me in the right direction with a comment in one of the other answers