Hi,

try to update as this

Also ensure you get the dates correctly

var gdt = new GlideDate();
gdt.setValue(grHRProfile.getValue('employment_end_date'));
var endDate = gdt.getByFormat("MMMM dd,YYYY");

var gdt1 = new GlideDate();
gdt1.setValue(grHRProfile.getValue('probation_end_date'));
var probDate = gdt1.getByFormat("MMMM dd,YYYY");     

if (grHRProfile.next()) {
    var hrProfileData = {
        employment_end_date: endDate,
        probation_end_date: probDate,
    };

Regards
Ankur