Tag question

had learnt "Tag Questions" in free English speaking class this evening. Lots of Canadians say "eh?" but we practiced saying, " You're Japanese, aren't you?" or " You were a bookkeeper, weren't you?" ...Since I had to think which tense was correct to use, it went like, " I'm working tomorrow, a a a aren't I ?" , " Nothing good came from the project, di di di did it?", " We have never been to your house, ha hav have we?". But most of students in class were in the same situation and we made all real conversaion with tag questions as well. After the class, the elevator was occupied with students and someone said "Let's call it a day, shall we?" which made me laugh.