One of the things I love most about the unschooling philosophy is the idea of learning about things as children show interest in them. Which is why we now have a calendar on our fridge. I've had the calendar for a while, but it only just recently made its way out, as Benjamin is constantly asking what day it is, what we are going to be doing tomorrow, and, most importantly, "Is Daddy home tomorrow?" It is only natural then, that we have a calendar to show us those things. I always loved doing the calendar with my preschool class, so I was excited to get this going with the kids. We don't do a formal calendar time or anything like that. Sometime during the morning (whenever I happen to think of it), I ask them to help me with the calendar, and we count all the numbers, ending with whatever today is, and add the new number. Then I tell them the day/date (as in, "Today is Sunday, September 22"), and we'll usually count the number of days until Daddy is "home for two days" as the kids say. And sometimes we'll talk about anything else we have going on in the next couple of days (like church, going to someone's house or going to play time at the library). It's just a couple of minutes in our day, something fun that the kids are interested in and enjoy, but at the same time we're learning numbers, counting, months, days, and other concepts of time (today, tomorrow, yesterday, before, after, etc.).
A funny side note: I've had to change the way I write some of the numbers. A while back, Benjamin informed me that my 4 and 9 were not right. I have always written an open 4, and I write 9 with a straight line, and apparently Benjamin was only familiar with the ways they're written here. I tried to tell him that both ways were fine, but he wasn't convinced. So I've had to adapt. =)