QA – Placement Quizzes | Calendars | Question 8

What was the day of the week on January 1, 2001?
(A) Sunday
(B) Monday
(C) Tuesday
(D) Wednesday


Answer: (B)

Explanation: The number of days left after dividing the period by 7 is known as odd days. Every ordinary year has 365 days i.e. 52 weeks and 1 odd day and every leap year has 366 days i.e. 52 weeks and 2 odd days. Every 4th year and every 4th century is the leap year.
100 years have 76 ordinary years and 24 leap years i.e. 76 + 2*24 = 124 odd days. = 7*17 + 5 = 5 odd days.
200 years have = 10 odd days = 7*1 + 3 = 3 odd days.
300 years have = 15 odd days = 1 odd days.
Since every 400th year is the leap year, 400 years have = 20 + 1 = 21 odd days = 0 odd days.
There are 0 odd days in 2000 years. Hence, there is 1 odd day up to the date January 1, 2001. Hence, it was a Monday.


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