How to reproduce

• connect to cms
• edit a content
• add a form
• add a simple text field, set rule Date
• save
• fill the form and let the date blank

Actual behavior

• A new page is displayed with:
  The form contains the following errors, please use the back function of your browser to go back to the previous page and correct it :
  Date ? : The value must be a date using the following pattern YYYY-MM-DD (for example 2010-12-31)
• the title of the page is messages_fr.xml

Expected behavior

• No new page when the date is invalid
• No page title messages_*.xml
• No error when the date is not mandatory and is empty
• the date should accept more than one pattern, for example YYYY/MM/DD or YYYY-MM-DD or...