aCalendar works with any calendar configured in Android: local and cloud.

You can create new local calendars in the calendar list.

When using local data (no matter if it is contacts, photos, calendars, etc) without backup you always risk complete data loss when the device breaks or gets lost.

Using local data should always mean to have a proper sync/backup solution working.

You can sync local calendar data in Android using 

We recommend to use cloud calendars instead of local calendars, especially when you have multiple devices.