Hi, we found a performance issue that occurs only in the "agenda" view, specially when events have several days of duration.

Look at this dojo.

https://dojo.telerik.com/@foxontherock/IZafonEW

In the "week" view, navigation from week to week is very fast.

In agenda view, it's very slow.

The issue is in that function: 

kendo.ui.AgendaView.prototype._tasks

On the 2nd loop, there's that call
task = event.clone();
and this one is repeated for each day of the event, even if the day to analyse is out of the agenda current period.

I think you can solve it by only looping the "visible" days of the current view.

In our case, events have several other fields not related to the agenda.  We are able to increase performance by removing them and only keep required ones, it's better, but still slow.

All others views performs very well with huge dataset / events on multiple days.