Question

how to do calender in mat

Answer 1

Concept of Odd Days

In an ordinary year there are 365 days, which means 52 x 7 + 1, or 52 weeks and one day. This additional day, is called an odd day. The concept of odd days is very important in calendars.

In a century - i.e. 100 years, there will be 24 leap years and 76 non-leap years. This means that there will be 24 x 2 + 76 x 1 = 124 odd days. Since, 7 odd days make a week, to find out the net odd days, divide 124 by 7. The remainder is 5. This is the number of odd days in a century.

You may memorize the following points related to the concepts of calendars to save time during the paper.

100 years give us 5 odd days as calculated above.200 years give us 5 x 2 = 10-7 (one week)-3 odd days.300 years give us 5 x 3 = 15-14 (two weeks)-1 odd day.400 years give us {5 x 4 + 1 (leap century)}-21}-0 odd days

Now, if we start from 1st January 0001 AD; for 0 odd days, the day will be Sunday; for 1 odd day, the day will be Monday; for 2 odd days, it will be Tuesday; for 3 odd days, it will be Wednesday and so on.

The following examples exhibit the application of the concepts explained above.

Concept of Leap Year

Every 100th year starting from 1st AD is a non-leap year, but every 4th century year is a leap year.Any year divisible by 400 will be a leap year e.g.: 1200, 1600 and 2000. And the years 1800, 1900 will be non leap years as they are divisible by 100, but not 400.

Example 1: What was the day on 9th February 1979?

Solution: You know that in 1600 years, there will be 0 odd days. And in the next 300 years, there will be 1 odd day. From 1901 to 1978 we have 19 leap years and 59 non leap years. So, the total number of odd days up to 31st Dec. 1978 is 19 x 2 + 59 = 97. On dividing 97 by 7 we get 6 as the remainder, which is the total number of odd days in these years. So, till 31st Dec. 1978 we have 1 + 6 = 7 odd days, which forms one complete week. Now, in 1979, we have 3 odd days in January, and 2 odd days in the month of February (up to 9th Feb). So, the total odd days are 3 + 2 = 5. Hence, 9th February 1979 was a Friday.