datePicker calendar will not display with 4 digit year

[undermensch]

If the date value is already set and returned by converter as 4 digit year, a javascript error is thrown and the pop up calendar will not display when clicking on the input.

[Melloware]

I would create a test case using PrimeFaces Test: https://github.com/primefaces/primefaces-test

Once you have a test case report it on the GitHub Issues page: https://github.com/primefaces/primefaces/issues