If you are not inclined to memorize, add, and subtract a long table of numbers, there is a much simpler method available to the casual date-figure-outer, that involves minimal memorization and math-skills. Let's say you want to figure out what day of the week October 16th, 2006 falls on.

Step 1: figure out the date of the first Sunday of every month of the year in question — or if you really don't want to work, just figure out the date of the first Sunday for the month in question. Taking the former route, we see that the first Sundays of each month in 2006, going right from January, are as follows: 1 5 5 2 7 4 2 6 3 1 5 3*

Step 2: add or subtract. For instance, if our month was February, we would see that the first Sunday falls on the 5th, so if we wanted to figure out what day the 1st falls on, we would simply figure out what day comes five days before Sunday, which is Tuesday. Going back to our example, we can leap through the weeks by adding 7 until we get close enough to do this. Since the first Sunday of October falls on the 1st and we want to figure out what day the 16th falls on, we add 7 twice, taking us to Sunday the 15th. After that, we just add 1 to take us to the 16th, which means the 16th is a Monday. 1 + 7 + 7 + 1, and you're done.

The most difficult aspect of this method is being able to conjure up the month you want: interested noders are advised to learn the "peg system" provided in improve your memory, as it both improves recall and is rather fun. Most people, though, will only need this for dates in the immediate future, so that isn't much of a problem.

Of course, given the increasing prevalence of electronic calendars these days, one can simply take out one's cellphone, but this method provides the advantage that it

  1. Impresses people who don't know about it (or a more advanced version)
  2. Doesn't end up giving you brain cancer if you use it too much(1) and
  3. Won't be rendered useless by an EMP attack.

Source: Your Memory: How it Works and How to Improve it, by Kenneth L. Higby

*Grouping these by twos or threes is suggested for ease of memorisation.1. Pending the results of a scientific study.