## Wednesday, 12 June 2013

### 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. 29th 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: 1st 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 1st January to 29th February, both the dates including): As given date i.e. 29th February 2000 falls in between 1st January to 29th 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 1st January to 29th 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. 20th 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: 3rd 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 1st January to 29th February, both the dates including): As given date i.e. 20th September 2000 does not fall in between 1st January to 29th 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 20th 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… :)

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