Explanation: 100 years have 5 odd days. Hence the last day of 1st century is a Friday. 200 years have 10 odd days or 1 week + 3 odd days. Hence, the last day of the 2nd century is a Wednesday. 300 years have 15 odd days or 2 week + 1 odd day. Hence, the last day of the 3rd century is a Monday. 400 years have 0 odd days. Hence, the last day of the 4th century is a Sunday.
