Well… We have finally studied each and every single step
in detail that we need to know while finding the day from any given date. And now
it’s time to test our knowledge. It’s time to test ourselves!!
I will take total 8
examples those will cover all the date cases you may encounter with.
For that I would like to revise all
the steps those we need to take into
account to find the day from date:
 Note down the date.
 Note down the key number for month.
 Find and note down the key number for first two digits in year.
 Find and note down the key number for last two digits in year.
 Add all the above noted numbers.
 Divide above addition by 7 and find the remainder.
 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).
 If the given date falls in between 1^{st} January to 29^{th} February and the 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!! But, 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, let's see each example one by one in detail.
Example
1. 12^{th} January 2013
Step 1. Note down the date: 12
Step 2. Note down the key number for month: January is always the 1^{st} month of the year so it’s key number is 1… (See Key Numbers For Month: 1^{st} Group)
Step 3. Find and note down the key number for first two digits in year: First two digits from 2013 forms 20. Key number for 16 is 0, 17 is 5, 18 is 3 and 19 is 1. So, for 20 it will be 0 as above sequence will repeat… See Finding The Key Numbers For First Two Digits In A Year:Quick Steps
Step 4. Find and note down the key number for last two
digits in year: Last two digits from 2013 forms 13.
 When we divide 13 by 4 we get quotient as 3.
 We subtract 1 from 13 and get 131=12.
 We add 3+12 and get 15.
 We divide 15 by 7 and get 1 as a remainder and this is the key number for 13.
For detail steps see Finding The Key Numbers For Last Two Digits In A Year
Step 5. Add all the above noted numbers: 12 + 1 + 0 + 1 = 14.
Step 6. Divide above addition by 7 and find the
remainder. If we divide 14 by 7 then we get 0 as a remainder (14 is present in
multiplication table of 7).
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. 12^{th} January 2013 falls in between 1^{st} January to 29^{th} February we need to check if the year 2013 is a leap year or not.
Last two digits from 2013 forms number other than 00 i.e. 13. So, we will check if 13 is completely divisible by 4 i.e. remainder is zero if 13 is divided by 4 (or we will check if 13 is present in the multiplication table of 4).
4 x 3 = 12
4 x 4 = 16
So, we can conclude that 13 is not completely divisible
by 4. And hence the year 2013 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 0 as a remainder. Therefore from the table below
the day on 12^{th} January 2013 is Saturday…!!!! Check your
calendar…!!! :)
SUN

MON

TUE

WED

THU

FRI

SAT

1

2

3

4

5

6

0

Example
2. 15^{th} August 2013
Step 1. Note down the date: 15
Step 2. Note down the key number for month: If we
subtract key number of May (i.e. 2) from key number of June (i.e. 5), we will
get key number for August i.e. 3 (52=3)… (See Key Numbers For Month: 2^{nd} Group)
Step 3. Find and note down the key number for first two digits in year: First two digits from 2012 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 2013 forms 13. And we have found the key number for 13 as 1 in previous example.
Step 5. Add all the above noted numbers: 15 + 3 + 0 + 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. 15^{th} August 2013 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 15^{th} August 2013 …!!
These were the two examples for dates falling in a nonleap year i.e 2013.
First date (12^{th} January 2013) was within 1st January28th February. While, second date (15^{th} August 2013) was outside 1st January28th February.
In the next post I will take two examples for dates falling in a leap year i.e. 2012
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These were the two examples for dates falling in a nonleap year i.e 2013.
First date (12^{th} January 2013) was within 1st January28th February. While, second date (15^{th} August 2013) was outside 1st January28th February.
In the next post I will take two examples for dates falling in a leap year i.e. 2012
Previous Index Next
how to calculate jan 1 2008 find day of the week?
ReplyDeleteHi Dinesh, thanks for your comment. For 1st Jan 2008, below is the calculation
ReplyDelete1 (Date) + 1 (key number for Jan) + 0 (key number for 20) + 2 (key number for 08) = 4. Now 4 indicates Wednesday. But, since 2008 is a leap year and the given date falls in Jan we need to go one day back. So, the day of week on 1st Jan 2008 was Tuesday! I have explained similar example in detail in next chapter for 5th Feb 2012. Check it out.