Have you been practicing the Day For Any Date in 2009 feat from last Sunday? This Sunday, we're going to push your mental skills with the calendar again, but in a different way!

Don't worry. We'll start slow. Our first project is an inexpensive calendar. How inexpensive? It's only 12 cents! This cheap perpetual calendar can be set up to show any calendar date. So where's the mental challenge? It's displayed in binary format! If you have Java installed, the web page will also show you how to properly display the current date.

Once you get the hang of reading binary dates, you can also try figuring out to read a free binary clock! If you need help, Wikipedia's Binary Clock page can help.

Moving to the next piece, we have a feat that will really help you come across as a calendar master! This is Walter Gibson's Magic Calendar (continues on another page). You hand someone a calendar page, and ask them to mark one day in each week of the calendar without you seeing their choices. You then ask how many Mondays were marked off, as well as how many Tuesdays, Wednesdays, and so on. When the spectator is done answering, you instantly give the total of the selected days!

We'll round this column out with some calendar puzzles courtesy of Ken Duisenberg:

1) Can you figure out a simple way to create magic squares starting from dates selected from a calendar?
2) Here's 3 puzzles in one, all of them concerning “calendar fractions”.
3) How is Ken's 6-block calendar constructed?

Those links should challenge you, and get you to look at the humble calendar in a whole new way. Of course, if you're interested in changing perspectives about the calendar, here's plenty of thought-provoking articles that will do just that.