I used to believe that when the clocks changed and people said we'd lose an hour or gain an hour, we lost or gained that hour every night at midnight.
Also, when people said their watch was fast, I thought it meant that the hands went round faster than normal.
A childhood belief about general

others believed things like this
- I used to believe that a quarter after the hour was 25 minutes after the hour because 25 cents = a quarter.— Marni
- I thought the big hand was for the hour and the smaller one was for the minutes until i was in third grade.— Time Challenged
- An hour and a half is exactly the same as half an hourAnon
- I used to believe that all songs were exactly a half-hour long.— Brian
- You had to wait an hour after eating ANYTHING, even one M&M, before swimming. Anon
- I was never able to get a good answere as to what hour of the day "evening" actually began— Tad