If it was a Monday on 1 January 2018, what was the day of the week on 29 December 2018?
Answer & explanation
Correct answer: option 1
The correct answer is Option (1) → Saturday
The weekday repeats every 7 days, so only the odd days, the days left over after whole weeks, move it forward. 2018 is not a leap year, so February has 28 days.
Odd days from 1 January to 1 December, month by month: January 3, February 0, March 3, April 2, May 3, June 2, July 3, August 3, September 2, October 3, November 2
Total \(=26\) odd days, and \(26=3\times7+5\), so 5 odd days
1 December 2018 is Monday + 5 = Saturday
29 December is 28 days, that is 4 whole weeks, after 1 December, so it is also a Saturday
Shortcut: A year that is not a leap year has 365 days, 52 weeks and 1 day.
So 31 December of such a year falls on the same weekday as 1 January: Monday
29 December is two days earlier: Saturday