This Alexa skill will test the user on his ability to calculate the day of the week based on a date.
It will start with a date from the current month, and progress to a date from the current year, the current century, and finally dates in the range from 1600-3000.
A good technique for finding the day of the week can be found in the book "Secrets of Mental Math" by Arthur Benjamin. There is also a description of the same method at http://gmmentalgym.blogspot.com/2011/03/day-of-week-for-any-date-revised.html.