The 19th of September 1987 was Saturday. What day was the 20th of September 1990 if 1988 was a leap-year? Choose one.
A) Monday	B) Tuesday	C) Wednesday	D) Thursday	E) Friday
There are 365 days in an ordinary year and 366 days in a leap-year.   365 divided by 7 (a week period) yields a remainder of 1, thus the same date after an ordinary year would fall on the next day of a week;   366 divided by 7 (a week period) yields a remainder of 2, thus the same date after a leap-year would fall two days after in a week;   Thus 3 years, 1988, 1989 and 1990, will accumulate   2+1+1= 
<gadget id="calculator">  2+1+1</gadget>
<output>4</output>
4 days, plus 1-day difference between 19th and 20th, which gives total of 5-day difference (5-day shift). Thus, 20th of September 1990 was Saturday+5 days=Thursday   Answer: Thursday
<result>D</result>
The 19th of September 1987 was Saturday. What day was the 20th of September 1990 if 1988 was a leap-year?