While getting a massage, I was sharing my recent trip to Japan with the masseuse and made some quip about her putting me to sleep through a combination of her skills and my jet lag. She asked what jet lag was, which was already a little odd to begin with, so I explained that because of the different timezones, my internal clock was all messed up because my sleep schedule whiplashed during the trip. After many a blank stare, I eventually came to the root of the problem: she actually thought every place in the world experiences daytime and nighttime at the same time. So either she doesn't understand how spheres work, or else she's a flat-Earther.
I've met people who thought every country experiences winter and summer at the same time of year, but I've never actually met someone before this masseuse who thought the entire world experienced daytime and nighttime at the same time.