Fonte ou source: http://www.evilmadscientist.com/article.php/perpetualcalendar
It’s Wednesday, the fourth day of the week. The binary number for 4 is 100. We use “heads” for 1 and “tails” for 0. So the left hand column has (top to bottom) heads-tails-tails = 100 binary = 4th day of week = Wednesday. (If you don’t already speak binary, no biggie. Start here or here and join us in a minute.)
It’s December, month 12, and 12 in binary is 1100, so the middle column is heads-heads-tails-tails.
Finally, the last column is all heads, since it’s December 31, and 31 decimal = 11111 binary.
You can, of course, gussy it up a bit beyond the cardboard. (“Be extravagant– use dimes!”)