Building on Robert's answer, I had to make a few edits to make it work for me, and additionally with use-package (placing it in a :config block).

;; change ical export, remove timestamp with regex
(require 'ox-latex)

(defun my-filter-timestamps (text backend info)
    "Remove timestamps from headings."
    (when (org-export-derived-backend-p backend 'icalendar)
      (replace-regexp-in-string "<[0-9]\\{4\\}-[0-9]\\{2\\}-[0-9]\\{2\\}[^>]*>" " " text)))  

(add-to-list 'org-export-filter-headline-functions
               'my-filter-timestamps)

And with my version I am not getting any "--" remaining. It looks great for me now in ical, but the export is much much slower. Glacial.

Building on Robert's answer, I had to make a few edits to make it work for me, and additionally with use-package (placing it in a :config block).

;; change ical export, remove timestamp with regex
(require 'ox-latex)

(defun my-filter-timestamps (text backend info)
    "Remove timestamps from headings."
    (when (org-export-derived-backend-p backend 'icalendar)
      (replace-regexp-in-string "<[0-9]\\{4\\}-[0-9]\\{2\\}-[0-9]\\{2\\}[^>]*>" " " text)))  

(add-to-list 'org-export-filter-headline-functions
              'my-filter-timestamps)

And with my version I am not getting any "--" remaining. It looks great for me now in ical, but the export is much much slower. Glacial.