## Arithmatical - Calendar

*Important Facts and Formulae*

**Definition**:

**a) Odd days :** The number of days more than the complete number of weeks in a given period is number of odd days during the period.

For example, a period of 10 days contains 3 odd days, 11 days contains 4 odd days, 12 days contains 5 odd days. But period of 14 days contains Zero odd days.

**b) Leap Year :** Every year which is divisible by 4 is called a leap year. But every century which is divisible by 4 is not a leap year. Every fourth century is a leap year

**c) ** An ordinary year has 365 days i.e (52 weeks +1).

**d)** A leap year has 366 (an ordinary year ) by 7, we get remainder 1, it means that it has 1 odd day.Like wise 366 days (leap year ) has 2 odd days.