Chapter 13. Few Important Tips!

Now you know how this method works.While performing this trick, you will first ask someone for a date for which he/she will already know the day of week falling. Then you will use the trick that you have learned so far and do the calculations and present the output day to the person who gave the date. And that person will be amazed to see that you have presented the correct date to him/her!!As simple as that!

But, sometimes people may ask the day for an invalid date. By invalid date I mean a date that doesn't exist. Example of an invalid date is 29^th Feb for a year which is not a leap year!Another example of an invalid date would be 31^st April. Now, April will always have 30 days only. So, 31^st April will never come!

For our convenience we will classify these invalid dates into two groups:

I. February will have either 28 or 29 days (in case of leap year). So, 29^th February will be an invalid date in case of all non-leap years!

II. Following months will always have 30 days only:

1. April
2. June
3. September
4. November

So, following dates will be invalid dates- 31^st April, 31^st June, 31^st September & 31^st November!

So, if the person asks you for a day of a date then make sure that before finding the day,  the date given is not an invalid date i.e. given date is not among any of the invalid dates mentioned in the above two groups!

That is to it!

One important thing again- We are using this trick for the dates those fall in Gregorian calendar only. And it is said that-Gregorian calendar came into existence from 24^th February 1582! So, we will calculate the day of any date which is falling after 23^rd February 1582..!! To know more about Gregorian calendar, click here!

Before I finish up let me tell you something –

While using this trick you may fail several times, you may make mistakes. I know this because even I have failed several times. I used to ask people for date of their choices (for which they already knew the day falling on those dates) and used to end up calculating the wrong day. And when I used to tell them the output; they used to laugh at me. But I never gave up. I learnt from those mistakes. I used to dig out my calculations and used to find out where I did the mistake. And I used to make note of all such mistakes so that I would not repeat them again. And now I can tell the day of any date accurately within few seconds…!!!

So, it’s my honest advice to you as well, never ever give up. Whenever you fall, get up. Just keep on trying and trying. And one day you will be amazed to see that you have mastered this trick...!!

Before performing this find day from date trick do practice a lot. It will boost your confidence… All the very very best.. :)

Previous                                            Index                                             

Chapter 12. Examples Explained : 29th February 2000 & 20th September 2000

In Previous post we saw two dates in the year 2100 which is a century year and also a non leap year. In this post we will see two dates examples in the year 200 which is a century year and a leap year as well.

Example 7. 29^th February 2000

Step 1. Note down the date: 29

Step 2. Note down the key number for month: 4 letters in January & February are common i.e. “uary”. Therefore, key number for February is 4… (See Key Numbers For Months: 1^st Group)

Step 3. Find and note down the key number for first two digits in year: First two digits from 2000 forms 20. Key number for 16 is 0, 17 is 5, 18 is 3, 19 is 1. The above sequence will repeat again. So, for 20 it will be 0…

Step 4. Find and note down the key number for last two digits in year: Last two digits from 2000 forms 00. We know that if we get a year in the format YY00 i.e. if last two digits form 00 then key number for 00 will always be -1.

Step 5. Add all the above noted numbers: 29 + 4 + 0 + (-1) = 32.

Step 6. Divide above addition by 7 and find the remainder. If we divide 32 by 7 then we get 4 as a remainder.

Step 7. Check if the year is a leap year or not (only if the given date falls in between 1^st January to 29^th February, both the dates including): As given date i.e. 29^th February 2000 falls in between 1^st January to 29^th February we need to check if the year 2000 is a leap year or not.

Last two digits from 2000 forms number 00. So, we will check if first two digits in year 2000 i.e. 20 is completely divisible by 4 i.e. remainder is zero if 20 is divided by 4 (or we will check if 20 is present in the multiplication table of 4).

4 x 5 = 20

So, we can conclude that 20 is completely divisible by 4. And hence the year

2000 is a leap year.

Step 8. If the given date falls in between 1^st January to 29^th February and the year is a leap year then we need to go one day back from our calculated final day to get exact day.. So from Step 6 our final day would be Wednesday (As 4 points to Wednesday). But, for this case we need to go one day back from our calculated final day to get exact day.. So, our final day would be one day before Wednesday i.e. Tuesday…!!

Example 8. 20^th September 2000

Step 1. Note down the date: 20

Step 2. Note down the key number for month: In Latin Septem means. We will subtract 1 from 7 and we get 6 i.e. key number for September… (See Key Numbers For Months: 3^rd Group)

Step 3. Find and note down the key number for first two digits in year: First two digits from 2000 forms 20 and we have already found the key number for 20 as 0 in previous example.

Step 4. Find and note down the key number for last two digits in year: Last two digits from 2000 forms 00. And we have found the key number for 00 as -1 in previous example.

Step 5. Add all the above noted numbers: 20 + 6 + 0 + (-1) = 25.

Step 6. Divide above addition by 7 and find the remainder. If we divide 25 by 7 then we get 4 as a remainder.

Step 7. Check if the year is a leap year or not (only if the given date falls in between 1^st January to 29^th February, both the dates including): As given date i.e. 20^th September 2000 does not fall in between 1^st January to 29^th February we don’t need to check if the year 2000 is a leap year or not. So, 4 is our final result. And therefore 4 points to Wednesday i.e. the day of week on 20^th September 2000 …!!

And thus we have covered all the expected date cases… I hope you have got the things cleared… To make yourself more comfortable and more confident, practice taking similar dates… :)

Previous                                            Index                                             Next

Chapter 11. Examples Explained : 28th February 2100 & 11th November 2100

Year 2100 is a century year. Also it is a non leap year. I will explain two dates in the year 2100 which are 8th February 2100 and 11th November 2100.

Example 5. 28^th February 2100

Step 1. Note down the date: 28

Step 2. Note down the key number for month: 4 letters in January & February are common i.e. “uary”. Therefore, key number for February is 4… (See Key Numbers For Months:1st Group)

Step 3. Find and note down the key number for first two digits in year: First two digits from 2100 forms 21. Key number for 16 is 0, 17 is 5, 18 is 3, 19 is 1. The above sequence will repeat again. So, for 20 it will be 0 and for 21 it will be 5…

Step 4. Find and note down the key number for last two digits in year: Last two digits from 2100 forms 00.

• When we divide 00 by 4 we get quotient as 0.
• We subtract 1 from 00 and get 00-1=-1.
• We add 0+ (-1) and get -1.
• We divide -1 by 7 and get -1 as a remainder and this is the key number for 00.

(Note: - If we get a year in the format YY00 i.e. if last two digits form 00 then key number for 00 will always be -1.)

Step 5. Add all the above noted numbers: 28 + 4 + 5 + (-1) = 36.

Step 6. Divide above addition by 7 and find the remainder. If we divide 36 by 7 then we get 1 as a remainder.

Step 7. Check if the year is a leap year or not (only if the given date falls in between 1^st January to 29^th February, both the dates including): As given date i.e. 28^th February 2100 falls in between 1^st January to 29^th February we need to check if the year 2100 is a leap year or not.

Last two digits from 2100 forms number 00. So, we will check if first two digits in year 2100 i.e. 21 is completely divisible by 4 i.e. remainder is zero if 21 is divided by 4 (or we will check if 21 is present in the multiplication table of 4).

4 x 5 = 20

4 x 6 = 24

So, we can conclude that 21 is not completely divisible by 4. And hence the year 2100 is not a leap year.

Step 8. If the given date falls in between 1^st January to 29^th February and year is not a leap year then the day corresponding to the remainder which we found from the Step 6 will be our final day!! From Step 6, we have got 1 as a remainder. The day on 28^th February 2100 is Sunday…!!

Example 6. 11^th November 2100

Step 1. Note down the date: 11

Step 2. Note down the key number for month: November is the first member of our 4^th group. So its key number will be 4... (See Key Numbers For Months: 4^th Group)

Step 3. Find and note down the key number for first two digits in year: First two digits from 2100 forms 21 and we have already found the key number for 21 as 5 in previous example.

Step 4. Find and note down the key number for last two digits in year: Last two digits from 2100 forms 00. And we have found the key number for 00 as -1 in previous example.

Step 5. Add all the above noted numbers: 11 + 4 + 5 + (-1) = 19.

Step 6. Divide above addition by 7 and find the remainder. If we divide 19 by 7 then we get 5 as a remainder.

Step 7. Check if the year is a leap year or not (only if the given date falls in between 1^st January to 29^th February, both the dates including): As given date i.e. 11^th November 2100 does not fall in between 1^st January to 29^th February we don’t need to check if the year 2013 is a leap year or not.

So, 5 is our final result. And therefore 5 points to Thursday i.e. the day of week on 11^th November 2100 …!!

Previous                                            Index                                             Next