We taught our daughter to count starting at zero. Her kindergarten teacher was not amused.

Great idea, and realize likely a joke, but wouldn’t you just need to pull the one or two that connect out to the internet?

Use the one built into iPhones and either encrypt iCloud so Apple cannot read it ( but no way to recover if you forget password) or turn off iCloud sync for health data (you will lose history with new phone).

Or, print out a one page annual calendar and use a pencil.