   :group 'timeline-tools
   :type '(list function))
 
+(defcustom timeline-tools-headline-time-format
+  "%Y-%m-%d %H:%M"
+  "Format of time used in the headline of a timeline."
+  :group 'timeline-tools
+  :type 'string)
+
 (defcustom timeline-tools-time-format
   "%Y-%m-%d %H:%M"
-  "Format of time as used by the formatting functions."
+  "Format of time used inside a timeline"
   :group 'timeline-tools
   :type 'string)
 

        (setq-local timeline-tools--current-time-end (org-time-string-to-seconds tend))
        (setq-local timeline-tools--current-files files)
        (setq-local timeline-tools--current-timeline timeline)
        (hl-line-mode)
        (buffer-enable-undo)
        (timeline-tools-redraw-timeline))

    (let ((timeline timeline-tools--current-timeline))
      (erase-buffer)
      (insert (format "* Timeline from [%s] to [%s]\n\n"
                      (format-time-string timeline-tools-headline-time-format
                                          timeline-tools--current-time-start)
                      (format-time-string timeline-tools-headline-time-format
                                          timeline-tools--current-time-end)))
      (insert "|--|\n")
      (insert "| Category | Start | End | Duration | Task |\n")
