If it was a Monday on 1 January 2018, what was the day of the week on 31 December 2020?
Answer & explanation
Correct answer: option 4
The correct answer is Option (4) → Thursday
The weekday repeats every 7 days, so only the odd days, the days left over after whole weeks, move it forward. An ordinary year of 365 days is 52 weeks + 1 day; a leap year of 366 days is 52 weeks + 2 days.
2018 is an ordinary year, 1 odd day: 1 January 2019 is Monday + 1 = Tuesday
2019 is an ordinary year, 1 odd day: 1 January 2020 is Tuesday + 1 = Wednesday
2020 is a leap year, and 31 December is its 366th day, 365 days after 1 January: 52 weeks + 1 day
31 December 2020 is Wednesday + 1 = Thursday
Tip: The last day of a year falls on the same weekday as its first day in an ordinary year, and one weekday later in a leap year.