Use TimeOfDay instead of DateTime for start and end time in CalendarEventData.

[PRBaraiya]

In the current CalendarEventData model, we are using the object of DateTime to define the start and end time of an event. But while manipulating the event, we are only using hours and minutes from the DateTime so, it is getting confusing. Because Users have to provide the date information even though it's not being used.

So, one solution that we can implement is to use TimeOfDay to store the start and end times.

We can deprecate some variables, that define the time span of an event and move it to a separate model. And in the next major version, we can completely remove it.

[mayank29malhotra]

I can work on this issue