When does it end?

Without a lot more information, it is impossible to answer your question. What are the nature of the calls? How often do you get them? What are your job responsibilities? What constitutes an emergency in your opinion? Etc.
If you are working for a park, there can be issues that arise that surely don't meet the normal definition of an emergency, yet can make a phone call a viable tool.
For example, the person that comes on after you may be looking for an item that you likely would have used and they can't find it. Or, something in a customer's site looks out of place and a quick call can help determine if it is something that needs attention. We have found that customers often claim they were told something by staff no longer on duty and it is often necessary to confirm what the customer is claiming (often it is not the whole truth). None of these come close to rising to the level of a life threating emergency, but as an employer I would not feel out of line contacting my employees to aid in completing the task at hand.
Now if your employer is contacting you in a drunken rant at 2AM that is a different animal.

Just answer politely, and say "I am sorry, we are entertaining company right now. Please call during our working hours."

Polite, concise, and he should get the message.

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If I'm not on the clock my calls and texts don't get answered. You have work hours for a reason. Respond to them during tomorrows work hours.