When people would use the term in the 40's, 50's 60's,etc. to describe the temperature outside. I thought it meant that was the decade people were acting like. Like if you said it's supposed to be in the 70's today, I would have thought there'd be men with afros, and women rollerskating outside! I finally figured it out after watching the weather channel one day.
A childhood belief about weather

others believed things like this
- I thought the term maiden name actually applied to women who were maidens.— Natasha
- I thought weather forecasters were psychic and that's how they knew what the weather would be.Anon
- I used to believe that when I went to movies people were behind the screen acting out the part — Amy
- I used to believe people really died in movies. I didnt understand they were just acting.— Justin
- I used to think that "cross-eyed" meant that people had X's for eyes, like dead people in cartoons.— Tim
- I used to believe that when people talked about 4x4 trucks, I thought it meant all the wheels turned.
— tracy