Can I use AnuCal with Apple Calendar (iCloud)?

There is no direct Apple Calendar connection yet, but you can bring an iCloud calendar in through Google. In the Calendar app on your Mac, hover over the calendar in the sidebar and click the share icon next to its name, tick Public Calendar, then copy the webcal:// link it shows. Anyone with that link can view the calendar, so use it for calendars you are comfortable sharing.

In Google Calendar, next to "Other calendars" choose + and then From URL, and paste the link exactly as it is. The calendar then appears in AnuCal under Google Calendar Sync, where you can tick it to show it on the year view.

The calendar comes in read-only, and Google refreshes subscribed links on its own schedule, so a new event can take a few hours to appear.