var x=$CS.getValue("WorkOrder_Fields_UDF_DATE1");
var y=$CS.getValue("WorkOrder_Fields_UDF_DATE2");
var z=y-x;
var a=z / (60 * 60 * 1000);
var b=z / (60 * 1000) % 60;
var c=parseInt(a)+" hours"+parseInt(b)+" minutes";
$CS.setValue("WorkOrder_Fields_UDF_CHAR1",c); ( Here Workorder_Fields_UDF_CHAR1 is the custom field which shows the Hours and minutes).
The above script if you input two Date and Time values, then the output will display in the below format,