The calendar only contains current and future events as of the publishing date. If an event ended before this date, it will not be in the calendar.
Download the calendar by using the DX4WIN Data Updater. Next, select File | Calendar from the main DX4WIN menu, then File | Import data dd/mm/yy from the Events calendar menu as shown:
Navigate to the location of the CALENDAR.TXT file, and open it to import the file into the DX4WIN calendar. Finally, File | Save Changes and exit.