Complete guide to Calendar problems for competitive exams: basic concepts of odd days (extra days beyond complete weeks), leap year (366 days, February 29 days), ordinary year (365 days), counting odd days in years (ordinary year = 1 odd day, leap year = 2 odd days), odd days in century (100 years = 5 odd days, 200 years = 3 odd days, 300 years = 1 odd day, 400 years = 0 odd days), finding day of week for given date, day codes (Sunday = 0, Monday = 1, Tuesday = 2, Wednesday = 3, Thursday = 4, Friday = 5, Saturday = 6), month codes for different months, concept of same calendar years (repetition of calendar), problems on finding next same calendar year, problems on finding day on a particular date, problems on number of odd days between two dates, problems on last day of century, problems on first day of year, and shortcut tricks for SSC, Banking, Railway, UPSC, and other government exams.