For the most part, by and large, the day after October 4 is October 5. This is not a particularly controversial statement. However, did you know that one year after October 4, they just skipped right over 10 days and went straight to October 15? Man, 1582 was a crazy year.
The reason is that 435 years ago the Gregorian calendar was implemented, and 10 days needed to be removed to sync the calendar back up with the seasons. I'm no scientist, but I'm pretty sure that means we've been living in the future this whole time