CalendarNotify

A simple add on that notifies you of pending calendar event invites, guild event sign ups and to notify you of player created events occurring "today". It will also provide a more noticeable 15 min. warning alarm for events that are beginning soon.

Or check out CalendarHUD

Notes:

• With patch 8.0 the calendar API doesn't  report the number of pending invites correctly until after they are selected in the calendar so that has been removed from the notice.
• The Alarm Event still doesn't seem to fire so there will be no event alarm messages.