Sorry, I am afraid the calendar has no support for entries dropped from a grid panel. It does not mean it is impossible though. It means it would require a considerable effort to customize the calendar, just that the feature is not provided out-of-the-box.
It would require to study the Calendar code and understand how it handles its internal events' dropping (events dropping that are already in a panel is supported) and then making specialized code for the drop. As grid panels are extremely flexible data-wise, I believe even with great support implementation, there will always be needs for specific behavior, as grid panels tend to have data specific to a scenario that will need to be "ported" to the calendar.
The main things (calendar-wise) that must be understood and extended are:
- how is set up a drop-target on the calendar, and how to bind arbitrary drag-sources to it
- how to programmatically add calendar entries to the calendar panel.
Once you can have the drag event trigger with the grid record, then you just need to bind the record relevant data to the calendar corresponding event (day on month view, day/hour in week view, or hour in day view).
Hope this helps!