Sometimes it isn’t easy to deal with Date format and comparing a date in JavaScript in MS Dynamics CRM.
Below is a simple function which takes a UTC date and then return back into a date only in formate YYYYMMDD.
In case you have a string date i.e. not a date then you can cast it into Date by using below
var completedOn = crmForm.formatedDate(completeDate);
// date format
crmForm.formatedDate = function(attr)
{
var parts = attr.split(/[T]/);
var fullDate= parts[0];
var dt = new Date();
parts = fullDate.split(/[-\/]/);
var y = parts[0];
var m = parseInt(parts[1]);
var d = parts[2];
var formatedDate =new Date(y + “/” + m + “/” + d) ;
return formatedDate;
}