Where Trigger The "please Enter A Valid Date." In Jquery.validate.js

I am using jQuery UI version 1.12.1 and jQuery Validation v1.15.0 I created a datepicker as follow: if ($.fn.datepicker) $(':input.date').datepicker({ changeMonth: true,

Solution 1:

Found it, it was actually trigger by a date method validation in jquery.validate.min.js, which is in line 1356:

// http://jqueryvalidation.org/date-method/
        date: function( value, element ) {
            return this.optional( element ) || !/Invalid|NaN/.test( new Date( value ).toString() );
        },