Thank you for your question.
I was not able to find any changes which can lead to this behavior. You might be using the code you have posted in a somehow specific scenario. Generally, the all-day cells are located in another element so you should use the following code to get them:
Point point =
DayViewAllDayHeader table = (
SchedulerCellElement schedulerCell = SchedulerUIHelper.GetCellAtPoint(point, table.Children);
The code snippet you have posted gets a cell from the table that is below the all-day area and should not be able to return all-day cells. Note that in both cases the point variable should be in control coordinates. This means that you only need to call PointToClient
if the e.X and e.Y are screen coordinates.
I hope this information will help you. If you still need assistance, please send me a complete source code which demonstrates your scenario. This will let investigate it and provide you with a solution.
Also, if you have any additional questions, feel free to ask.
All the best,
the Telerik team