Basically there are 365 days in an ordinary year, which means 52*7+1 day or 52 weeks plus one day per year. This concept is applicable only for years excluding the leap year. Concept of Odd days: Whenever we are asked to find out a day of the week on a specific date, we use the concept of ‘odd days’ Odd days may be defined as the number of days more than whole weeks. Leap Year: If it is not a century, then each year divided by four is a leap year. One point also to be noted here is that leap year comes in every 4â€™th century.

Formula or Rule for solving CALENDAR questions

100 years give us 5 odd days

200 years give us 5 x 2 = 10 â€“ 7 (one week) 3 odd days.

300 years have 5 x 3 = 15 â€“ 14 (two weeks) 1 odd day.

400 years have {5 x 4 + 1 (leap century)} â€“ 21} (three weeks) 0 odd days.

January has 31 â€“ 28 = 3 odd days.

February has 28 â€“ 28 = 0 odd day in a typical year and 1 odd day in a leap year and so on for all the other months.