When I was in kindergarten, my teacher used to play records to the class. One taught the days of the week, but for some reason (I suspect it must have been to confuse little kids), the song started with Monday. So, naturally, I thought all the calendars were wrong. I went home and tried to convince my mother that Sunday was the last day 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 always thought that after 1999 it would be 1990 again, but with different months and days of the week
— optional - I once refused to believe in Thursday. I'd heard there were seven days in a week, but could only name six.Anon
- I used to believe that the Chinese boy in my kindergarten class flew from China every day to get to class.— Debi
- I thought the guy who got shot at the beginning of Gunsmoke was replaced every week by a live guy.— Monica
- When I was in kindergarten, I used to believe that they locked the teacher's in the teacher's lounge at night.Anon