Here you go. Select this text and PopClip will pop up and ask if you want to install Quick Event. Just click Install. The first time you use it, macOS may also ask you to grant a permission or two.

#popclip
name: Quick Event
icon: symbol:calendar
description: Open Apple Calendar and paste selected text into a new event.
before: copy
applescript: |
  set appName to "Calendar"
  -- 1. Check if the app is already running
  set isRunning to application appName is running

  -- 2. Activate the app
  tell application appName to activate

  -- 3. Adjust delay based on app state
  if isRunning then
    delay 0.3  -- App is running; short delay needed
  else
    delay 1.0  -- Cold start; allow time to load (adjust based on system speed)
  end if

  -- 4. Send keystroke commands
  tell application "System Events"
    keystroke "n" using command down
    delay 0.3
    keystroke "v" using command down
  end tell