I used to believe that summer vaction lasted a year (that is how long it felt to me). I was very upset when I found out how long it really was.
A childhood belief about general

others believed things like this
- I thought that 1983 went on for 3 years - had to ask my sister who decided how long a year lasted.— Sally
- When I was in elementary school I use to think that teacher lived at school at their desks all year long.Anon
- I used to think a female daddy-long-legs was called a "mummy-long-legs".Anon
- the summer that I turned 11 I waited out side on the step all summer for my hogwarts letter... ;D — Ginny weasley... not really
- I used to think the lyrics of "Boys of Summer" said "poison summer"— Lindsay
- I used to believe that eg 1+1=11 and 2+2=22.
Luckily that only lasted until age 2 1/2.— Madi