keeping calendar data off Google?

Is there a way to use Avast Mobile Security to prevent the android phone calendar from syncing its data with Google’s website? I’ve used Avast’s firewall to block all internet and data access to calendar and calendar storage but that does not prevent syncing?

Related question: Is there a calendar/Agenda app I could use on an android phone that does not send data anywhere and keeps it on the phone?

Thanks.

Go to Settings > Account settings > uncheck Calendar and take it off the sync.

Did you block sync manager, google framework and other services connected to google calendar?