Please consider this post a follow-up to my previous post about mnemonics. The other day I taught myself the number of days in each month of the year. While I’m a little embarrassed to admit that I had gone all these years without learning it, the method used is one worth sharing. … At least I was embarrassed. Everyone I talked to told me that they don’t know the days of the month either. You should all be ashamed of yourselves. Note: no stupid rhymes were involved in learning this.

Based on the previous post, one could take an image corresponding to each month, or to that month’s number (making January a tie, per the major system), and that would have worked, but I wasn’t in the mood to make eight distinct mental images for meat (31). With this method we can condense it down to two words / one image.

What I did first was look at a calendar of the entire year as one table. If you do that then you’ll notice that only three numbers pop up: 28, 30, and 31. No month has 29 days (except February on leap year), and no month has 32 days. February is the only month with 28 days, except for leap year. Since I already knew February, that leaves only 30 and 31 days, which gives us a binary. If you’re familiar with binary, feel free to skip the next section. If not, you need to read this in order to understand what I did next.


The base system refers to the way that we represent numbers. It is how every known number comprised of a set of digits (e.g. 12345) is computed. For any base n, you need 0 through (n-1) symbols. What most people consider numbers is in fact base ten, which uses the digits 0 through 9. The reason it is called base 10 is because, say, 12,345, is in fact 5 * (10^0) + 4 * (10^1) + 3*(10^2) + 2*(10^3) + 1*(10^4). Each digit is multiplied by a power of ten (10 is the base, the power is the exponent).

There are other bases, though. For instance base 3 uses the digits 0 through 2. 201 in base 3 is 1*(3^0) + 0*(3^1) + 2*(3^2), which in base 10 is 1 + 2*9 = 19. For bases higher than ten, people started borrowing the alphabet. For instance in base 16 (a.k.a. hexadecimal), 0-9 is  0-9, but 10-15 is a-f. Sometimes in programming you will see things labelled in hex, as it allows you to go from 0-255 using two digits instead of three (255=ff in hex).

So, if we apply this same logic to the base 2 system, then we can build any number out of zero and one. For instance, 111 = 1*2^0 + 1*2^1 + 1*2^2 = 1 + 2 + 4 = 7. Try using this to count on your hands! Because the addition of each digit increases the amount of numbers you can represent twofold: on one hand you count to 31; using both hands you can go over a thousand.

So feel disdain for the plebs who can only reach ten on their fingers!


So looking at a table of the months, you have


If you use 1 to represent 31, and 0 to represent 28 and 30, you get
101 = 1*2 + 1*2^2 = 5
010 = 1*2^1 = 2
110 = 1*2^1 + 1*2^2 = 6
101 = 5

Converting from binary to decimal this makes 5,2,6 and 5 again. We have now condensed the months of the year, 12 sets of two digit numbers, into 4 single digit numbers. From there we can use the major system with 5(L)-2(N)-6(Ch-Sh or J sound)-5(L). For this I used Lawn-Chill. You could imagine the house where you grew up, you’re chilling on the lawn, and everything is encased in ice. You can’t move. You feel so cold.

Initially I screwed this up and imagined a lawn covered in snow. When the picture came back to me later, I kept thinking “Lawn slush?”, “Lawn snow?”, “Lawn White?” I knew all of those were wrong, but the right word just wasn’t coming. When you use a symbol to represent something, pick one such that when the same image appears vividly in your mind two months later, you know exactly what it means.

As a backup image I used “Luna-shale”. To avoid future confusion (Luna or just Moon?) I imagined a moon with a giant pair of boobs. (Remember, mature and memorable are inversely correlated). For shale, i imagined spurts of black American shale spouting from Luna’s boobs. I also imagined seashells on the misshapen moon, to reinforce the “Sh” sound in “Shale”, as opposed to just “Oil” or “Gasoline”. At this point I have an image that I couldn’t forget even if I wanted to.

Congratulations! We have taken the numbers 31,28,31,30,31,30,31,31,30,31,30,31, and condensed it down into one mental image. Unfortunately, retrieving the information requires doing all of these steps backwards. Everything has it’s trade-offs, but on the bright side, you get a lot of practice with binary!