Which are the weird wall calendar events that will change your calendar?

We know there's a lot to talk about with wall calendars — and that includes all of the cool things that will come with them, such as the wall calendar that's your friend's mom's birthday, the calendar that pops up on your phone to say "I'm doing this" when you visit a friend's house, or even the calendar you're going to hang out with at the bar.There are so many ways to use a wall calendar, so...