Presidential Calendar Mnemonic (PDF coming soon)
Chapter 1: A Simpler Method
Chapter 2: Mod7 Magic
Chapter 3: The Recipe
Chapter 4: Ten Months
Chapter 5: Zanuary and Zebruary
Chapter 6: US Presidential Elections
Chapter 7: Silly Stories
Chapter 8: Mastery
This is the fifth post in a series describing the Presidential Calendar Mnemonic. Our goal is to calculate the day of the week, given any date in any century. By the end of this chapter, we’ll be able to do that for all twelve months of three years: 2024, 2025 and 2026.
In Chapter 4, we skipped January and February, and here’s the thing: There are no month codes for either one! They are simply undefined. So what are we to do when asked about January or February? The good news is we have overlays for them, day-for-day, with imaginary months called Zanuary and Zebruary1. These are two-month extensions of the previous year. Zanuary 2025 lays perfectly on top of January 2026. Likewise, Zebruary 2025 lays perfectly on top of February 2026. Since we don’t have codes for January and February, we use the month codes for the imaginary matches. If we are given February 12, 1941, we know Zebruary 1940 will yield the same result.
Zanuary and Zebruary month codes are 5 and 1, respectively. Notice this is the same pattern as May (5) and June (1), if that helps. With these two months, we now have 12 month codes:
January: UNDEFINED. See Zanuary of the previous year
February: UNDEFINED. See Zebruary of the previous year
March: 0 (No ma’m) 🚫 (No ma’m) March ≡ November
April: 3 (Jefferson’s April shower) 🌧️🌧️🌧️ April ≡ July
May: 5 (May flowers with 5 petals) 🌺🌺🌺🌺🌺 May = Zanuary
June: 1 (Washington’s June bug) 🪲 June ≡ Zebruary
July: 3 (Jefferson’s fire crackers) 🧨🧨🧨 April ≡ July
August: 6 (or -1) (Augustus Ceasar drowning under water) ➖1️⃣
September: 2 (Adams’ 2 piles of autumn leaves) 🍁🍁 September = December
October: 4 (four Halloween trick-or-treater) 👻👻👻👻
November: 0 (No ma’m) 🚫 March ≡ November
December: 2 (Adams’ 2 Christmas trees) 🎄🎄 December ≡ September
Zanuary: 5 (Five winter gloves)🧤🧤🧤🧤🧤 Zanuary ≡ May
Zebruary: 1 (Washington’s zebra) 🦓 Zebruary ≡ June
Why does this work? Because we are putting leap days (if any) at the end of our mnemonic year, where they can’t do any mischief. By putting leap days at the end of our mnemonic year, we simply don’t care about leap years!2
Every other calendar mnemonic I’m aware of needs you to be aware of leap years and make exceptions for January and February of those years. The rules for determining leap years aren’t super complex3, but our minds are already taxed with remembering multiple codes and doing mod7 work. It’s better to eliminate leap year steps from our workload.
Let’s practice January and February dates. What day is January 1, 2025?
Zanuary 1, 2024 will yield the same results
monthType = ⎡ y+c+m ⎤ = ⎡ 4+0+🧤🧤🧤🧤🧤 ⎤= ⎡ 9 ⎤ = 2 (Press two fingers)
DOW = ⎡ 2 + ⎡ 1st ⎤ ⎤ = 3 (Wednesday)
What day is February 1, 2025?
Zebruary 1, 2024 will yield the same results
monthType = ⎡ y+c+m ⎤ = ⎡ 4+0+🦓 ⎤= 5 (Press all five fingers)
DOW = ⎡ 5 + ⎡ 1st ⎤ ⎤ = 6 (Saturday)
What day is February 12, 2026?
Zebruary 12, 2025 will yield the same results
monthType = ⎡ y+c+m ⎤ = ⎡ 5+0+🦓 ⎤ = 6(-1) (Press pinky finger)
DOW = ⎡ -1 + ⎡ 12th ⎤ ⎤ = ⎡ -1 + 5 ⎤ = 4 (Thursday)
This is a natural stopping point for those who are satisfied knowing the calendar for only 2024, 2025, and 2026. You are done! It will be impressive enough to magically conjure the day of the week for any day between March 1, 2024 and February 28, 2027 (Zebruary 2026). Yet for those who want to master the whole modern calendar, there is more to learn. It’s a challenge, but this is the easiest method I know. Buckle up and let some American history do the heavy lifting for us.
We need different names to emphasize we need to use the year code from the previous year. The letter Z reminds us these months go at the end.
The only reason to know leap years is if someone is trying to trip you up with a non-existent date. They might say “What day is February 29, 1900?” There is a way, however, of knowing if 1900 is a leap year without knowing the leap year rules. Calculate the days for February 28th (Wednesday) and March 1 (Thursday). They don’t skip over a day so the 29th does not exists. So 1900 is not a leap year. This is ironic because instead of the mnemonic requiring us to know leap years, our mnemonic does the opposite. It can actually answer the question “Is this a leap year?”
Leap years are generally those that are divisible by four. The year 1960 is divisible by 4, but 1950 is not, so year 1960 is a leap year and 1950 is not. Exceptions are made if the year is also divisible by 100. The years 1700, 1800, and 1900 are divisible by 100, so they are exceptions to the “divisible by 4” rule, and therefore they are not leap years. Also, there are exceptions to the exceptions. If a given year is divisible by 400, it is an exception to the exception “divisible by 100” rule, so the year is in fact a leap year. So 1600, 2000, and 2400 are in fact leap years, even though they are divisible by 100. In other calendar mnemonics, after navigating those rules, one would subtract 1 from the month codes for January and February. So instead of using month codes 5 and 1, January and February would temporarily have month codes 4 and 0. In our system, imagining Zanuary and Zebruary as an overlay of January and February eliminates all of these rules.
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