This site provides a calendar feed which can be consumed by calendar programs. The feed is available at If you'd rather add one calendar per theater, you can find per-theater calendars under "Per-Theater Feeds" in the navigation bar at the top of the page.

To add the calendar(s) to Google Calendar, follow these instructions.
To add the calendar(s) to Apple Calendar, follow these instructions (Mac) or these instructions (iPhone or iPad).

There's also a web calendar for today and the next two days available here.