I used to think that the multiplication table on the back of my notebook was a calendar. I used to cross off the days until I noticed that it would become a smaller date. I assumed it was another month then.
I thought one month had 144 days, but the days went by very randomly (12, 24, 36..)
A childhood belief about counting

others believed things like this
- back in the days i thought the world was black and white like in the pictures— compaq
- I thought that "tomorrow" was one of the days of the week— Frank
- I thought that days had 100 hours in them. Very surprised to hear there were only 24.— Cassiopeia
- I always thought that after 1999 it would be 1990 again, but with different months and days of the week
— optional - i used to believe that if you got barked at by a dog you would die in 45 days— woza
- I use to believe that peeing was bad for your body, and it should only be done once per 3 days— Master P