June 1, 2001 is a Friday. What day is September 1 The main formula

June 1, 2001 is a Friday. What day is September 1 The main formula


30+31+31=92,
92 / 7 = 13, more than 1,
5+1=6,
So it's Saturday



How many days are there from September 10, 2012 to April 2, 2013?


10. 12, 1, 3 are all 31 days, 124 days
11 is 30 days, 2 is 28 days, September 10th to April 2nd includes 10th but not 2nd, September is 21 days, April is 1 day
124+30+28+21+1=204