When I was about 4, my mother taught me the names of the days of the week, she said "I have an idea, lets call today Tuesday, and tommorow Wednesday, etc". Until I was in 3rd grade, I would argue with kids, claiming that my mother invented the names of the days of the week!
A childhood belief about general

others believed things like this
- I thought that "tomorrow" was one of the days of the week— Frank
- I once refused to believe in Thursday. I'd heard there were seven days in a week, but could only name six.Anon
- I always thought that after 1999 it would be 1990 again, but with different months and days of the week
— optional - I believed that my mother invented toast.— Helen
- I used to believe that my mother invented peanut butter and jelly sandwiches. Anon
- At the age of around five, I realized that my mum's and dad's names were not mum and dad!— yelloworpurple