Hello Santhana
Please try below. g_form doesnot work server side
(function calculatedFieldValue(current) {
var dateString1 = new GlideDateTime(current.begin); //make sure variable name is begin
var dateString2 = new GlideDateTime(current.end); // make sure variable name is end
var diffSeconds = gs.dateDiff(dateString1, dateString2, true);
diffMins = diffSeconds/60;
return Math.round(diffMins); // return the calculated value
})(current);
Please mark my response as correct and helpful if it helped solved your question.
-Thanks
