At 12 am someone in my school said “good night morning”, then someone replied with “nighty morning”, and then everyone decided to say “nighty morning” at 12 am. It carried on to next year which is when everyone else got to find out about it, and I decided to spread it to here. They had a rulebook, then lost it, so they made a new one, which I copied here:

https://wasteof.money/posts/63fab629bac4b7a8034e0f60