No of Days Calculation is getting reduced by One Day

If you only work with full days, you can switch to eventEndSpec="Date" mode which will translate the end date to "end of day":

https://doc.daypilot.org/scheduler/event-end-date-time/

But that will not work for half-day cells used in this tutorial.

So what could be the way around then? i tried changing the value from 720 to 1440 but that distorts the table

You can change the config like this (keep the rest of the properties unchanged):

var dp = new DayPilot.Scheduler("dp", {
  scale: "Day",
  cellWidth: 40,
  // ...
});