Calendars

Calendar Important Formula’s

  • 1 ordinary year = 365 days = (52 weeks + 1 day.)
  • 1 ordinary year has 1 odd day. 1 leap year has 2 odd days. = (76 x 1 + 24 x 2) odd days = 124 odd days.

Remember the Number of days in a Months for calendar.

Months having 30 days in a month.

  1. April
  2. June
  3. September
  4. November

Months having 31 days in a month.

  1. January
  2. March
  3. May
  4. July
  5. August
  6. October
  7. December

Special Month : February

  • Depending on whether the year is a leap year or not.
  • Leap years are exactly divisible by 4
  • February can have : 28 Days  or 29 Days (For Leap Year)

Formulas Summary for Calendars:

  •  A leap year has 366 days
  • Every year divisible by 4 is a leap year, if it is not a century.
  • Every 4th century is a leap year and no other century is a leap year.
  • Counting odd days
    1 ordinary year ≡ 365 days ≡ (52 weeks + 1 day)
    Hence number of odd days in 1 ordinary year= 1.
    1 leap year = 366 days = (52 weeks + 2 days)
    Hence number of odd days in 1 leap year= 2.
    100 years = (76 ordinary years + 24 leap years)
    = (76 x 1 + 24 x 2) odd days
    = 124 odd days.
    = (17 weeks + 5 days)
    = 5 odd days.
    Hence number of odd days in 100 years = 5.
    Number of odd days in 200 years = (5 x 2) = 10 = 3 odd days