Examples:
"I'm going to study until 8PM" Is he going to stop studying at 8PM sharp or 8:01PM?
"I'm not going to study until 8PM" Is he going to start studying at 8PM sharp or 8:01PM?
"I'm working until Friday" Does he stop working after his work on Thursday or Friday?
"I'm not working until Friday" Does he start working at Friday or Saturday?
"The kidnappers have given us until October 11th to deliver the documents" Do they need to deliver the documents before it hits October 10th or 11th?
From other similar posts, I learned that until is mostly exclusive but it can sometimes be inclusive but how do I tell exactly?