##
What Day Is It?
*May 3, 2022*

*Posted by nrhatch in Humor, Magick & Mystery, Mindfulness.*

comments closed

comments closed

The Great Courses lecture series is an extensive collection of home study courses in areas of Art, Science, Math, Philosophy, Brain Fitness, etc. Our local library offers a number of the Great Courses on DVD, often with an accompanying handbook.

One series that contains some FUN “party tricks” is *The Secrets of Mental Math, *presented by Professor Arthur T. Benjamin (an “engaging, entertaining, and insightful” lecturer).

From Professor Benjamin’s series of 12 lectures on Mental Math, I learned, *inter alia*, tips on **Calendar Calculating**.

What’s that, you ask?

**Calendar Calculating** allows you to determine the day of the week for a specific date without flipping through a calendar.

*Note: Some of you will get a kick out of Calendar Calculating. Others will wish to stick with a paper calendar to check the day of the week for a given day. *

*To each his own.*

The basic formula is: **Month Code** + **Date** + **Year Code** (minus multiples of 7) = **Day of the Week**.

*(Month, Day of the Week, and Year Codes are discussed below.)*

A quick example:

**July 4, 2022** = 5 (month code) + 4 (date) + 6 (year code for 2022) = 15

From that sum, subtract “14” (to eliminate multiples of 7). The resulting sum of “1” means that July 4th this year will land on a **Monday . . . **

Go ahead. Check your calendar. We’ll wait.

**Huzzah! A 3-day weekend for those of us in the USA celebrating our independence!**

Here’s another example from this year:

**October 31, 2022** = 6 (month code) + 31 (date) + 6 (year code) = 43 – 42 = 1 = **Monday**

Reminder: Some of you will get a kick out of Calendar Calculating. Others will wish to stick with a paper calendar to check the day of the week for a given day.

*No judgment from me.*

**Days of the Week Codes (these are pretty obvious):**

Monday = 1

Tuesday = 2

Wednesday = 3

Thursday = 4

Friday = 5

Saturday = 6

Sunday = 7 (or 0 because 7-7 = 0)

In order to perform the calculations quickly, you will need to memorize 12 **Month Codes. **It helps to have a quick pneumonic device for each month:

January = 6 (W-I-N-T-E-R has 6 letters) (January = 5 in a leap year)*

February = 2 (2nd month) (February = 1 in a leap year)*

March = 2 (March **2** the beat!)

April = 5 (A-P-R-I-L or F-O-O-L-S has 5 letters)

May = 0 (Hold the May-0)

June = 3 (June B-U-G)

July = 5 (F-I-V-E-R Works!)

August = 1 (“A” is the 1st letter of the alphabet)

September = 4 (F-A-L-L has 4 letters)

October = 6 (T-R-I-C-K-S or T-R-E-A-T-S has 6 letters)

November = 2 (in the US, Thanksgiving = 2-rkey day)

December = 4 (X-M-A-S or L-A-S-T has 4 letters)

*In a leap year, January has a code of 6 – 1 = 5 (because no leap has occurred yet) and February has a code of 2 – 1 = 1 (for the same reason).

Example: January 1st, 2000 (**a leap year**) = 5 + 1 + 0 = 6 ~> **Saturday!**

The “why” behind these code numbers is due to the length of each month. Since 28 days is a multiple of 7, February and March start on the same day of the week (EXCEPT in a leap year) because February has 28 days (EXCEPT in a leap year).

The rationale for the other months is similar:

March has 31 days which is 3 days longer than 28 so we add 3 to the code for March (2) to calculate that April’s code = 5.

April has 30 days which is 2 days longer than 28 so we add 2 to its code of 5 to get “7” for May. After subtracting out 7 (to reduce by multiples of 7), May’s code is “0.”

*As I noted above: Some of you will get a kick out of Calendar Calculating. Others will wish to stick with a paper calendar to check the day of the week for a given day. I hear ya. *

*So does Goofy!*

**Year Codes**

To calculate the Year Code for a specific year, the formula is **Year** (just the last 2 digits) +** Leap Years** (divide the year’s last 2 digits by 4 and ignore the remainder) + **Year Code for the Century. ** The resulting sums are reduced by multiples of 7. Why? That’s just the way it is.

Here are the **Century Codes**:

1600 = 0

1700 = 5

1800 = 3

1900 = 1

2000 = 0

Example: The **year code for 2022** = 22 + 5 (22/4 = 5 leaps)+ 0 (century code) = 27 – 21 (to reduce by multiples of 7) = 6

Just for fun, calculate today’s date to see if it conforms:

**May 3, 2022** = 0 (Month Code) + 3 (date) + 6 (year code) = 9 – 7 = 2 and 2 = **Tuesday**

GO YOU! You are catching on QUICK!

*Note: Some of you will get a kick out of Calendar Calculating. Others will wish to stick with a paper calendar to check the day of the week for a given day. *

*For those of you who want to dive in . . ..*

Here are the year codes for the first 32 years this century:

2001 (1) 2002 (2) 2003 (3) 2004 (5) 2005 (6) 2006 (0) 2007 (1) 2008 (3)

2009 (4) 2010 (5) 2011 (6) 2012 (1) 2013 (2) 2014 (3) 2015 (4) 2016 (6)

2017 (0) 2018 (1) 2019 (2) 2020 (4) 2021 (5) 2022 (6) 2023 (0) 2024 (2)

2025 (3) 2026 (4) 2027 (5) 2028 (0) 2029 (1) 2030 (2) 2031 (3) 2032 (5)

Since **year codes repeat every 28 years** (from 1901 through 2099), for years like 2030, you can delete multiples of 28 to make mental calculations easier:

October 31, 2030 = 6 + 31 + 2 (year code)= 39 – 35 = 4 = **Thursday**

The same is true for the last century ~ reduce the year (1998) by multiples of 28:

1998 – 28 = 1970 – 28 = 1942 – 28 = 1914

Due to the repeating nature of year codes, July 4, 1998 fell on the same day of the week as July 4, 1970, July 4, 1942, and July 4, 1914.

As a result, it’s easiest to reduce to 1914 first and then calculate the year code:

14 (year) + 3 (14 / 4 = 3 leaps) + 1 (century code for 1900) = 18 – 14 = 4 is the year code for 1914 . . . as well as for 1942 & 1970 & 1998.

And that makes sense:

If the year code for 1998 = 4 . . . then the code for 1999 = 5 . . . and the code for 2000 (a leap year) = 5 + 2 = 7 – 7 (to reduce by multiples of 7) = 0 and we know that’s correct since we know that the year code for 2000 is 0.

Returning to our Calendar Calculation, you’ll be happy to know that** July 4, 1998 **fell on a Saturday:

5 (Month Code) + 4 (Date) + 4 (Year Code) = 13 – 7 = 6 = **Saturday!**

You are getting the hang of this! Take a bow!

The year codes repeat every 28 years (from 1901 through 2099) because the calendar shifts 28 times for the years PLUS 7 times for the leap years: 28 + 7 = 35. Since 35 is a multiple of 7, the days of the week stay the same.

1900 and 2100 are NOT leap years.

**Quick Tip:** To perform Calendar Calculations as a party trick using Mental Math, start by calculating the Year Code before asking for the Month and date.

If someone born on December 25, 1960 wants you to calculate the day of the week they were born, ask for the Year first:

Year code = 1960 – 28 – 28 = 1904 = 4 + 1 (leap) + 1 (century code) = 6

December 25, 1960 = 4 + 25 + 6 = 35 – 35 = 0 =** Sunday**

And, if they’re wondering, being born on a Sunday is good news (at least for those of certain religious persuasions):

*Monday’s child is fair of face*

*Tuesday’s child is full of grace*

*Wednesday’s child is full of woe *

*Thursday’s child has far to go*

*Friday’s child is loving and giving*

*Saturday’s child has to work for a living*

*And the child who is born on the Sabbath Day, is bonny, blithe, good and gay.*

OK, that’s it.

Go forth and calculate!

*Foot Note: Some of you will get a kick out of Calendar Calculating. Others will wish to stick with a paper calendar to check the day of the week for a given day. *

*Mickey is OK with that. So am I!*

**Aah . . . Math is FUN-da-mental!**