Let me teach you how to mentally quickly figure out the day of week of any date in history

To make it easier, let's just do any date from 1700 to 2018. I'll explain more later, but I don't want to lose too many people by making it more complicated. This is fairly simple once you understand the process... just basic adding is all that is required and a little bit of memorization. Also, it's easier to do with pencil and paper (or text on your computer) to keep track of some numbers while you're learning the process.

Okay, here we go.

To start with, let's give every day of the week a number and memorize it.

Monday = 1, Tuesday = 2, Wednesday = 3, Thursday = 4, Friday = 5, Saturday = 6, and Sunday = 0

Now, let's give each century a number from 1700 to 2000's like I stated above, and memorize these four numbers. So:

1700's = 0, 1800's = 5, 1900's = 3, and 2000's = 2

Now, there is a little more memorization here, but it's easy. You're going to need to memorize 12 dates... one date for each month of the year, and I'll tell you how to easily remember them in a minute. These are called "Doomsday Dates". First, here are the dates:

1/3 (or 4), 2/28(or 29), 3/14, 4/4, 5/9, 6/6, 7/11, 8/8, 9/5, 10/10, 11/7, 12/12

Now before you crap your pants, this is simple to remember. The easy way to remember these is starting in April, all the even months are the same day as the month. So 4/4, 6/6, 8/8, 10/10, 12/12. Simple. Starting with May, remember the odd dates by the phrase "working 9 to 5 at the 7/11" Which means the odd months will be 5/9, 7/11, 9/5, and 11/7. Simple. To memorize the final three dates, March 14th is easy because it's "pi"... 3/14. February is just the last day of the month... the 28th (or 29th). And just remember January 3rd (or 4th). I'll explain why it could be the 3rd or 4th or 28th or 29th in a minute.

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Okay, now let's pick a date! How about July 4th, 1776.

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Now, there's 5 numbers we need to figure out. It's simple. Here we go:

1. First thing we're going to do is look at the century. It's the 1700's, so remember the number you memorized for the 1700's? It's a 0. So write a zero down.

2. Next thing to do is look at the year of the century... in this case, it's 76. See how many times the number 12 goes into 76. Don't ask questions, just do it. You're always going to use the number 12 here on this step no matter the date. The answer is 6 times. Write a 6 down.

3. Now what's left over after? 12 goes into 76 six times to give you 72. That's 4 left over. Write a 4 down.

4. Now how many times does 4 go into that leftover 4? You're always going to use the number 4 on this step regardless of the remainder amount. So the answer here is 1. 4 goes into 4 one time. Write a 1 down.

5. Okay, great work. Now, remember those doomsday dates I told you to memorize? We're going to use that now. The date we are figuring out is July 4th, 1776. So we need to look at July. The July date I told you to memorize is 7/11. So what you want to do is count how many days of the week July 4th is from July 11th. July 4th is seven days from July 11th. So that means July 4th falls on the same day of the week as July 11th. So mark a 0 down. If it was July 5th, you'd mark a 1 down because it's a day short of a week from your doomsday date of July 11th. If we wanted to figure out July 27th, you'd mark a 2... because you'd count by sevens from the doomsday to get to July 18th, then July 25th, and then you'd get the 2 because it's two days from July 25th. A little complicated to explain, but I hope you get it. So again, mark a 0 down.


So, now we got FIVE numbers:

0
6
4
1
0

Add it up and get:

11

Now, how many times does 7 go into 11? (You'll always use the number 7 here just like you used the number 12 on step two and 4 on step four.)

7 goes into 11 one time. What's left over?

Four. Four is what's left over. What day of the week is the number 4? Look at the days of the week numbers I told you to memorize.

Thursday. The answer to what day of the week July 4th, 1776 is... is Thursday.


It takes a lot of words to explain, but it's a very simple and easy process once you understand. It really only takes you maybe 20 seconds to do it in your head. And less if you get really good at it.