If you use Saturday = 0, like Conway does, instead of Sunday = 0, then your month_day table becomes 1, 4, 4, 0, 2, 5, 0, 3, 6, 1, 4, 6.<p>Martin Gardner gave a good suggestion for making that easy to memorize. Group it into sets of 3, giving<p><pre><code>  1 4 4
  0 2 5
  0 3 6
  1 4 6
</code></pre>
You can memorize the first three lines as 12^2, 5^2, and 6^2, and then just have to remember that the last line is 2 more than the first.