How to Calculate the Day of the week of any given date in no time. It's a calendar calculation technique that I learned from a book. By Practicing it allows you to take a date, like 15 August 1947, and mentally calculate which day of the week it fell on.

Note : “Mod” means to divide the number and keep only the remainder. For Example if the Total of all codes is 58 mod 7, then divide 58/7 and keep only the reminder i.e. 2

**The Year Code**

To calculate the Year Code, use this formula:

**YY**is the last two digits of the year. For the year 1947, it’s 47.

First, divide

**YY**by 4 and discard the remainder: 47 div 4 = 11.

Then add 11 back into the

**YY**number, which is 47 in this case, resulting in 58.

The next step is: 58 mod 7. We’ve divided 58/7 and left with a remainder of 2. That is the Year Code for 1947.

Hold that in memory while you calculate the items below.

**The Month Code**

This is easy — just memorize the number

**033614625035**:

Memorize it as (

**033**)(

**614**)(

**525**)(

**035**)

**The Century Code**

Just remember the number

**4206420**:

(

**420**)

**6**(

**420**)

**Leap Year Code**

Note : The other thing to take into account is whether you are dealing with a leap year. If the date is from January or February of a leap year, you have to subtract one from your total before the final step and for other months except Jan and Feb.

If you can divide a Gregorian year by 4, it’s a leap year, unless it’s divisible by 100. But it is a leap year if it’s divisible by 400.

1992 is a leap year because you can divide it by four.

1900 is not a leap year because you can divide it by 100.

2000 is a leap year because you can divide it by 400. Calculating the Day

**Back to the original formula:**

(Year Code + Month Code + Century Code + Date Number – Leap Year Code) mod 7

For 15 August 1947, here are the results:

Year Code: 2

Month Code: 2

Century Code: 0

Date Number: 15 (the 15th of the month)

Leap Year Code: 0

So:

(2 + 2 + 15) mod 7 = 19 mod 7 = 5

Match the resulting number in the list below, and you’ll have the day of the week:

0 = Sunday

1 = Monday

2 = Tuesday

3 = Wednesday

4 = Thursday

5 = Friday

6 = Saturday

15 August 1947 was on a Friday.

**Leap Year Example**:

Lets calculate the Day for 18 July 1996

Year Code : 1 (96/4=24+96=120, 120 Mod 7 = 1)

Month Code : 6

Century Code: 0

Date Number : 18

Leap Year Code : 0 (No minus because it doesn't fall in Jan and Feb)

So:

(1 + 6 + 18) mod 7 = 25 mod 7 = 4

18 July 1996 was on a Thursday

**Another Leap Year Example :**

**1 January 2000: Start with ’00, leaving a Year Code of zero.**

January has a Month Code of zero.

The Day Number is 1.

The Century Code for dates in the 2000s is 6.

2000 is a leap year, since it can be divided by 400, and the date is in a January or February, so subtract 1 from the total in the final step.

Answer: 0 + 0 + 1 + 6 – 1 = 6.

1 January 2000 was a Saturday

**Today's**

07 November 2017

Year Code : (17/4=leaving reminder we get 4) (4+17 Mod 7 = 0) because reminder is zero

Month Code : 3 (November)

Century Code : 6 (year falls in 2000 century)

Leap Year : 0 (No 2017 is not a leap year)

So.

(3 + 6 = 9 Mod 7 = 2)

Right Today is Tuesday

Hope you find this post useful, If you have any questions, please leave a comment below.

## 3 Comments

Leap year oru confusion und. 2016 year nov 15

ReplyDeleteCan't read the text given in boxes

ReplyDeleteChanged CSS, now you can read text in the box

Delete