Something I've learned is the anchor method for multiplication of two, two-digit numbers. It may seem complicated at first, but it's actually incredibly powerful. First consider the product to be found as a product of two sums, each one "anchored" to a nearby round number. This product can be written as

*(a + c)(a + d) = a^2 + ac + ad + cd*

*(a + c)(a + d) = a(a + c + d) + cd*

where

*a*is the anchor. From the right-hand-side of the last line above, the anchor is multiplied by itself with the sum or difference terms

*c*and

*d*. Then the correction term

*cd*is added or subtracted, depending on whether the signs of

*c*and

*d*were the same or not, respectively.

For example, consider the product 17 * 18. This can be written as (20 - 3) * (20 - 2) = 20(20 - 3 - 2) + (2 * 3) = 306. The algorithm is easy to carry out because the first product is 20 * 15 = 300. Cool stuff.

The information for the calendar can be found here: http://myreckonings.com/wordpress/2010/11/22/a-2011-%E2%80%9Clightning-calculation%E2%80%9D-calendar/. It's very nicely done and I highly recommend it for all those mentats in training =)