We have found a problem that some of our date action parameters trigger the jQuery unobtrusive validation when the input loses focus, while others do not.
We then found that the ones that work have got default values populated.
We tracked the problem down to the fact that jQuery validation uses the following line:
When we inspect the rendered markup, we find the input elements for the date parameters that have default values, has this attribute: "data-val=true", while the ones without default values does not have the attribute at all, and that would seem why
jQuery validation does not get triggered on those.