when I was much younger (I'm 21 now) I went through a short phase when I thought everybody had a birthday every month rather than once a year. I have no clue where I got the idea.
A childhood belief about birthdays

others believed things like this
- My parents have the same birthday -- month, day, and year. I though all mom's and dad's had the same birthday.— Cait
- i used to think that if i didn't celebrate my birthday each year my younger sister would catch up with me— q
- i thought I got one year older when my family sang the birthday song.— I am the ghost
- Since the girls name Jackie is short for Jacqueline, I thought the boys name Jack was short for JackalAnon
- My birthday was on a different day every year, assigned by my parentsAnon
- I used to think that your birthday changed every year, and that your parents just decided what day it was.— Daniel