Having "Days" eliminated a lot of sibling squabbles and provided opportunities for teaching us to do chores, rewarding us, and having fun. Despite the chores, we each always loved when it was our Day. During special times, like the month of December you got to do the advent calendar when it was Your Day. That was my favorite thing.
I've put my own advent calendar up now and it's just mildly fun, since I'm the only one who really cares about it. But someday, I'll have little tykes who will hopefully get a kick out of it just like I did when I was little.
If you don't have one, it's not too late to put one up! Making your own is pretty simple. To help you out I've put together some of my favorite DIY advent calendars that you can get ideas from.