I tested latest 18.104.22.168 for the international date fields.
When i enter a field in Dutch in format '3 maart 1965', it will not be saved (at least it is not displayed). Entering it as '3 March 1965', it is saved as '3 maart 1965', but the next save will remove the date from the field.
I have following setting in wordpress-general: j F Y and the strict-format setting in the plugin is selected.
Hope this helps solving it.