Cannot save a date property if the date format is locale-dependent and the wiki locale doesn't match the JVM locale

Follow this steps to reproduce:

• Make sure your wiki is multilingual
• Make sure the list of supported locales includes one that doesn't match the locale of the JVM (or Operating System). My JVM/OS uses 'en' and so I added 'fr'.
• Create an application with AWM that has a date property. In the second step (Application Structure), after you add the date property, set the date format to "MMM-yyyy" (without the quotes)
• Switch to French language (or whatever language you added to the list of supported languages), e.g. by adding "?language=fr" to the URL of the application home page.
• Add a new application entry
• Make sure the list of months provided by the date picker is in French (force reload the page if not)
• Choose a date using the date picker. E.g. "Fév-2015"
• Save.

The date is not saved.