1. Odd Days
A number of days more than the complete weeks are called odd days in a given period.
2. Leap Year
A leap year has 366 days.
In a leap year, the month of February has 29 days.
Every year divisible by 4 is a leap year if it is not a century.
Examples: 1952, 2008, 1680 etc. are leap years.
1991, 2003 etc. are not leap years
Every 4th century is a leap year and no other century is a leap year.
Examples: 400, 800, 1200 etc. are leap years.
100, 200, 1900 etc. are not leap years
3. Ordinary Year
The year which is not a leap year is an ordinary year.
An ordinary year has 365 days
4. Counting odd days and calculating day of any particular date
1 ordinary year ≡ 365 days ≡ (52 weeks + 1 day)
Hence a number of odd days in 1 ordinary year= 1.
1 leap year ≡ 366 days ≡ (52 weeks + 2 days)
Hence a number of odd days in 1 leap year= 2.