This calendar is hosted on Google Calendar, and if you use a digital calendar, you can probably integrate into your own, so that PTA events appear automatically right next to your personal events.
To integrate this calendar into your own Google Calendar, copy the following URL, then go to Google Calendar, click the arrow next to “Other calendars,” click “Add by URL,” and paste it: http://www.google.com/calendar/feeds/meuct2qfvnpr6cc6bgj95hk434%40group….
To integrate this calendar into your own iCal, copy the following URL: http://www.google.com/calendar/ical/meuct2qfvnpr6cc6bgj95hk434%40group.c…
One or the other of those links should work for almost any other calendar program.
Also see the printable PDF version of the 2012-2013 ICSD calendar (no PTA events included).