When you have good dreams that are pure during the day. Pure is for the type of dream. It will have to be a positive dream to be pure. Dreams for the pure dreams you will have. Day for the time you will have the dream. Has to be during the day.
Can be abbreviated to PDD
Teacher: "Your sleeping!"
"Sorry. I was having a Pure dreams day."
Mom: "Wake up!"
"Sorry, I had a PDD."