If your Jenkins instance is running in a different location than your own (for example: the server is in NY but you are in LA), then the NY time zone will most probably be used. This may be quite annoying if you need to compare build dates.
To see the time zone currently set, go to
jenkins_server/systemInfo and see the
user.timezone system property.
You may want to change the time zone displayed to match your own time zone. By going to your user configuration page, you can set the
User Defined Time Zone to match your own.