**Calendar** is a way to display relationships between day, month and year.

Every year that divides by four is leap year and all other ordinary years are there. In the ordinary year there are 365 days and 366 days in Leap year i.e. in a simple year, total 52 weeks and 1 day, and in one leap year there are 52 weeks and 2 extra days.

** Normal and Solar Year **

The main and smallest unit of time measurement is the day. The timeline of one day is equal to the time spent in a whole round on the Earth’s axis and when the earth takes a full circle of the Sun, then the time taken is equal to one solar year.

One solar year = 365 days, 5 hours, 48 minutes and 47½ seconds is equal to approximately 365.2422 days. It was revised to 365 days as the year which was called ** General Year .**

** Leap years **

A normal year is 365 days and a solar year of 365.2422 days. In this way, every normal year is less than 0.2422 days from the solar year. If the year is calculated on the basis of 365 days, then every year, the average year will be less than 0.2422 days from the solar year. Thus the importance of calendar will be reduced. If this sequence continues for 4 years, the normal year in this period will be 0.2422 × 4 days from the solar year i.e. ‘0.9688 days. This period is equivalent to about 1 day. Thus, after every 4 years, it is added in the form of an amendment, the 1st day is added in the month of February, which is February 29 and the year is 366 days. Thus we can say that the year which is completely divided from 4 or the centenary year which is completely divided from 400, is called leap year; Eg -1996, 2000, 2004, 2016 etc.

In the leap year, both the first day of the year and the last day are uneven, i.e., the last day increases one day compared to the first day of the year; For example, if a leap year is the first day i.e. January 1, then the last day of the same year i.e., will be on Thursday, December 31.

** Centenary Leap Year **

Leap year comes every 4 years. Hence leap year 4 is contained in the multiplier. Thus, if the number of the year runs from 4, it will be leap years, but this rule does not apply in the century. Century leap year comes 400 years. These are multiples of 400 years. Thus, if it is a part of 400 in the century year, then it will be a year leap year.

** cycle of days **

The seventh part of any week is called day. There are 7 days in a week. Monday, Tuesday, Wednesday, Thursday, Friday, Saturday and Sunday. A cycle of weeks is completed in seven days. After this, the days start getting recursive again. .

The 28th, 30th, or 31st of any month, or 365th of the year, is called ** Date .** This is determined by numbers.

** Context of Odd Days **

Extra days left after this full cycle of days are called odd days – if starting from Monday, then 1 full cycle and 1 extra day or 1 asymmetrical day will be available in 8 days time period. One day after one full moon comes in one full circle. After this, the days start getting recursive again.

Any day after the full cycle of seven days of the day, it is called a heterogeneous day. Therefore, to find the odd days, divide the number of days by 7. The quotient (or bar) that is received in this part of the part indicates towards the full chakras of the days and the remainder which indicates the days of the odd days.

Number of days of odd days in 14 days = 14 = 2 times 0 remaining

= 0 days

Number of days of odd days in 20 days = 20/7 = 2 times 6 remaining

= 6 days

Number of days of odd days in 30 days = 30/7 = 4 times 2 remaining

= 2 days

Number of days of uneven days in 365 days = 365/7 = 52 times 1 remaining

** ⇒ Notes – The number of odd days can not be greater than 6.**

** Use of Odd Days **

To know which day will be on a certain date, it is necessary to use a heterogeneous day. The beginning of the seventh century is Monday, that is, on 1st January 1st of Monday. Therefore, on the first day of Monday and the last day of Sunday, in the 7-day cycle of relation with the seventh century, it is Sunday.

**Calendar related important facts **

** (i)** One Normal Year = 365 days = 52 weeks + 1 day = 1 Asynchronous day

** (ii)** one leap year = 366 days = 52 weeks + 2 days = 2 odd days

** (iii)** 100 years = 76 ordinary years + 24 leap years

= (76 + 24×2) Heterogeneous day

= 124 Asynchronous day

= 17 weeks + 5 days

= 5 Odd Days

** (iv)** In 200 years the number of odd days 2 * 5/7 = 1 time 3 remaining = 3 days

** (v) **In the 300 years the number of days of heteroscope -2 times 1 remaining = 1 day

** (vi)** The number of odd days in 400 years

4 x 5 = 20 days

Because the fourth century is leap years. Therefore, the number of odd days is to add 1 more: Number of odd days in 400 years

20+ 1/7 = 3 times remaining 0

= 0 days

So there is no odd day in 400 years.

** (vii)** 31 days of the number of days uneven 31

= 3 = 4 times 3 remaining

= 3 days

** (viii)** The last day of a century can not be Tuesday, Thursday or Saturday but it can be Wednesday, Friday and Sunday.

** (ix) **The first day of a century can be on Monday, Tuesday, Thursday or Saturday.

** (x) **If there is any date of any month in a normal year or if there is any war, then the next year will be more than one on the same date of the same month. Like – If on Monday, January 1, 2001, will be on Tuesday, January 1 in 2002.

In each leap year (half year) (xi) , the rate of any particular day or date will increase from 2 i.e. i.e. Saturday on January 1, 1996, then on Monday, January 1, 1997.

** (xii)** The last day of the normal year is the same as its first day i.e. if it is January 1, then on 31st December of that year it will be only on Thursday and on 1st January of next year Will happen. If Leap is January 1 of the year, then on Saturday, December 31, that year will be Saturday.

** (xiii) **7 Number of days to go back = number of days to move forward

** (xiv) **The role of ‘after’, ‘before’, ‘before’ and ‘before’ are very important in the words related to the questions related to this chapter. So its information is necessary.

If the word ‘after’ has been used to find a date or day in any question, then it is necessary to know the desired time by increasing the day from the given time; For example, what will be the date after 4 days of March 15, so here is the date after the 4th day of March 15. 15 + 4 + 1 = 20 March Similarly, on the third day of Thursday, on the day after Thursday, three days after tomorrow, ie the fourth day will be Monday. Apart from this, if there is a question ‘before’, ‘before’ or ‘after’, then the time is reduced or increased as long as the question is given in the question, as on Thursday, three days before -There was a day, so here it is three days before Thursday, Thursday-3 i.e. Monday. Similarly, the date will be 5 days after August 12, so here it means 12 + 5 i.e. 17th August.

** (xv) **The number of days total is 7 in each week Therefore, on any day, adding or adding 7 days to any day is received again the same day.

**The questions asked in this chapter are generally divided into four parts.**

** (a) **A question **based on different dates** was given up to date requested or after the date

Total number of days up to date / 7 before date of date

On knowing – If it is a complete part, then on the date you ask, it will be on the date given in the question.

** (b) Based on the year intervals **will be asked under it First of all, in the questions, the difference between the two years given is known. The number of leap years in which the difference between the two dates is obtained is then added. Then they are divided by 7. If the remainder comes to zero, then it will be the same day, if the remainder is obtained in the digits, then if you ask about the later days, by decreasing or when asked about later days, find the desired answer.

** ( c) Questions on the Mixed Problem **The first of the questions asked under the years given on the basis of the interval rules given above Let’s know the day of date. Then, on the date of the date, the date of the desired date is determined based on the rules of the different months given above.

** ( d) Based on the basic calendar **question Before solving these related questions, it is necessary to keep in mind that in which century the leap year is 31 December, Sunday, the centenary year after the centenary leap year, December 31, Friday, December 31, the centenary year, December 31, the centenary year, December 31, then the centenary year leap The year Oga. So it will be Sunday 31 December. Similarly, the centenary leap year will be the 31st of the centenary year. The following facts have been expressed for explanation of the above facts

31 December 1600 – Sunday

31 December 1700 – »Friday

31 December 1800- »Wednesday

31 December 1900 – Monday

31 December 2000) – »Sundays

**TYPE 1
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**Example:** If the 11th day of the month is Saturday, which of the following days will occur five times a month?

** (a) **Tuesday** (b) **Sunday

** Solution: (c) **According to the question, if the 11th day of the month is Saturday then (11-7) = 4 date will also be Saturday. In this way, 4 will arrive five days before date, i.e. five times in the month of Friday, Thursday and Wednesday.

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