The last day of a century is 31 December of a year such as 1900 or 2000. On which of these days of the week can the last day of a century NEVER fall?

Explanation

1. 01

   100 years have 5 odd days, 200 years have 3, 300 years have 1 and 400 years have 0.

2. 02

   So the last day of each century, counted from day 0 = Sunday, is day 5, 3, 1 or 0: Friday, Wednesday, Monday or Sunday.

3. 03

   Tuesday, Thursday and Saturday can never be the last day of a century.