Languages for Timer Events differs in BPMN2 Modeler and jbpm-designer.
Default offered languages in BPMN2 Modeler:

• Java
• Javascript
• Rule
• Xpath
• mvel

There is missing the most important language for timer events: cron
User has possibility to add any expression language manually, however it would be nice if the cron language was present between default expression languages by default.

Please note that in the jbpm-designer user has no possibility to specify custom expression language and jbpm-designer doesn't support nor Java, nor Javascript, nor Rule, nor Xpath, nor mvel for timer events.