Date Picker & Time Picker Conditions in Javascript

Date Picker & Time Picker Conditions in Javascript

I have telerik Rad Datepicker & Time Picker.I wanted to check when someone
select Startdate Before Enddate & Also start time before Endtime Here i
use for that,
Start Date : 1/31/2013
End Date : 1/1/2013
Start Time : 10:00:00 AM
End Time : 11:00:00 AM
In the above example StartDate & EndDate is wrong but Starttime & EndTime
is correct.Like this scenario my below code doen't show the error.
My Javascript Code is
function validatenow(sender, args) {
debugger;
var StartDateControl = $find("<%= rdpStDt.ClientID %>");
var SD = new Date(StartDateControl.get_selectedDate());
var EndDateControl = $find("<%= rdpEd.ClientID %>");
var ED = new Date(EndDateControl.get_selectedDate());
var StartTimeControl = $find("<%= rtpSt.ClientID %>");
var ST = new Date(StartTimeControl.get_selectedDate());
var EndTimeControl = $find("<%= rtpEt.ClientID %>");
var ET = new Date(EndTimeControl.get_selectedDate());
args.IsValid = true;
if((SD > ED ) || (ST > ET)){ //if startdate or time is larger than
enddate or time it shows the error.
args.IsValid = false;
}
}