To delete a Calendar item, you first have to select the item you want to delete.

If you are viewing the Calendar in the Day view, after selecting the specific item you want to delete, choose  Edit    Delete  

If you are viewing the Calendar as Week or Month, click on the item's action button  Delete   .

If you are viewing the Calendar as Year, you cannot delete items.

Note:
When you delete any object in BSCW, it first goes to your WasteBasket. Thus, if somehow you have deleted the wrong item of your calendar, you can undelete it, using this function on your WasteBasket.

Attention:
Inform all invited participants before deleting an appointment: edit the appointment and use the option [attach a personal note] in order to inform the participants. They will not be automatically informed!