31 Party or not?

The other week I told kids I was going out after dinner.  Laney asked where, and I replied, "Aunt Cathy is having a 31 party, so I am going to that."  Laney quickly replied, "Uh...don't you mean a 41 party?  I would think its going to be more like a 41 party."

I explained to her that this is a party for a company called 31 and not a birthday party.  She felt much better, Cathy on the other hand, did not.