Bookmarks save dates in your calendar for quick reference (i.e., Campaign Start, Milestone Event, etc.). Previously created bookmarks are viewable to everyone in the calendar and any user role can create them, plus, individual users can rearrange bookmarks to suit their own needs.
Creating a New Bookmark
Select the Book icon next to the word "Bookmarks". Enter the name of your desired bookmark. Select the date of your book. Click Ok.