[TYPO3-mvc] Validate DateTime and customizing of flashMessages

[Boris Meier]

Hi together

How can i validate a date input in a form? 

In the yxzValidator the object is already created and therefore before the validator starts, I get the exception: "Conversion to a DateTime object is not possible. Cause: DateTime::__construct() [datetime.--construct]: Failed to parse time string (01.01.19894) at position 10 (4): Unexpected character"

Second question: How can I customize the flashMessages in a proper way? 

Thanks for your help

Boris