This has to be changed in two places:

In WEB-INF/validation.xml it must be set in this section towards the top of the file. This is used to validate any dates that are input through the UI.

<constant>
	<constant-name>DATE_PATTERN</constant-name>
	<constant-value>dd/MM/yyyy</constant-value>
</constant>

In the WEB-INF/classes/Messages.properties file it must be changed under the date.format key. i.e. date.format=dd/MM/yyyy