Validator on input date Time field

Summary

Validator on input date Time field

Content

Hi,

We have a date range on our Search form and we are validating the dates using validator property of <oj-input-date-time> (custom function is written). 

It is checking the date range is startDate < endDate and should not be in future. But in some cases after changing the values in these input boxes multiple times, these validators are not getting called. Is there any way to call these validators explicitly ? 

Also can we throw error on a specific component of VBCS from javascript?

Also please advise if there is any javascript function available to check the validating of date e.g. 30th Feb is Invalid Date.