I use to believe that on some days, or dates, the day would change in the middle to another day.
three points of evidence were:
(1) towards the latter week of the
month of some calanders, Sunday, Monday, Tuesday and sometimes Wednesday would have a slash through the square for the date with one date (eg 22) in the top half and another (eg 29, seven days later in the lower half.
(2) the clock wad divided into two 12 hour sections (AM vs PM) which repeated, and on the days that switched in the middle, the switch occurred at noon, with the PM 12 hour section to facilitate the crossover
(3) my folks would often ask each other what day of the week it was (eg "Is is Tuesday today"), with the resonse being "Yes, all day). Well, clearly then on other days the day must have changed.
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 - 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
- i used to believe that if you got barked at by a dog you would die in 45 days— woza