SharePoint's calendar app/list (Classic view) is pretty good, but leaves a lot to be desired. Calendar overlays are clumsy to work with, and it's difficult to build calendars that can dynamically and intuitively filter by certain criteria (list columns).

We've found for certain projects that a K2-based calendar would help us, especially if it had certain features:

• Use Rules to filter events by the values of SharePoint columns. Let the value of a filter dropdown control what events are shown on the calendar.
• Allow or disable creation of new events based on the values or aggregate values of other events within date ranges. For instance: For all events at Location A (column value), between a certain Friday and Sunday (date range), add up the Cost field. If it adds up to more than a given threshold set for Location A in another SharePoint list, disallow creation of the event.

** Also: if an event with a specific column value already exists within a given date range (e.g., "Event Type = Wedding") disallow creation of other Wedding events in that range.

• Find a more elegant way to visualize lots of events on the month view of the calendar grid. Users often miss events under the "Show more" dropdown.
• When filtering calendars, SharePoint doesn't give an easy way to clear the filter or go back to the previous state. An easy enhancement over SP.
• Built-in color coding of events according to column values (not just what calendar they're on).
• For bonus points, the ability to drag and drop events into new timeslots to update them.

This could be a real value add above what SharePoint currently does, and having it native rather than needing a K2 add-in would set developers' minds at ease.

Thanks for listening!