Math Short Notes: Calendars

Calendars and Odd Days  

Odd Days: Remainder obtained when dividing the number of days by 7.  

- Leap Year:  

  - Has 366 days.  

  - Every year divisible by 4 is a leap year (if not a century).  

  - Every 4th century (divisible by 400) is a leap year; other centuries are not.  

- Odd Days Calculation:  

  - 1 ordinary year = 365 days = 52 weeks + 1 odd day  

  - 1 leap year = 366 days = 52 weeks + 2 odd days  

- 100 years:  

  - 76 ordinary + 24 leap years  

  - Odd days = (76 × 1) + (24 × 2) = 124 = 17 weeks + 5 odd days  

- Odd Days Summary:  

  - 100 years = 5 odd days  

  - 200 years = 3 odd days  

  - 300 years = 1 odd day  

  - 400 years = 0 odd day