How to Counting of weeks and days in year:
(a) 1 ordinary year has 365 days = 52 weeks + 1 odd day
(b) 1 leap year has 366 days = 52 weeks + 2 odd days
(c) 100 years = 76 ordinary years + 24 leap years = 76*1 + 24*2 = 124 odd days
= 17 weeks + 5 odd days
(d) Since in 100 years, number of odd days are 5
(e) In 200 years, number of odd days are 5*2= 10 = 1 week + 3 odd days, 3 odd days
(f) Similarly in 300 years 5*3 = 15 = 2 weeks + 1 odd day
(g) Similarly for 400 years number of odd days 5*4 + 1 = 0 odd days, from this we conclude that for 800, 1200, 1600 , 2000, 2400 years odd days will be zero