What was the day of the week on 1st January, 2006?
Answer & explanation
Correct answer: option 2
The correct answer is Option (2) → Sunday
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, so the same date falls 1 weekday later the next year; a leap year of 366 days moves it 2 weekdays.
Every 400 years make whole weeks, so the first 2000 years leave 0 odd days: 31st December 2000 was a Sunday and 1st January 2001 a Monday. Counting year by year from there:
2001 is an ordinary year, 1 odd day: 1st January 2002 is Monday + 1 = Tuesday
2002 is an ordinary year, 1 odd day: 1st January 2003 is Wednesday
2003 is an ordinary year, 1 odd day: 1st January 2004 is Thursday
2004 is a leap year, 2 odd days: 1st January 2005 is Thursday + 2 = Saturday
2005 is an ordinary year, 1 odd day: 1st January 2006 is Saturday + 1 = Sunday