Find the day | How to Find the day of specified date | Important interview aptitude question

What was the day of the week on 16th July 1776?
1776 July 16th =(1775year+period of 1 January to 16 July 1776)
(First find the nearest leap year (because it contain 0 odd days-see the formula)
1775=1600+175 years-equation 1
175=100+75 years –equation 2
From equation 1
1600 year contain 0 odd days
And 175 year 100+75
100 year contain 5 odd days
75 years =(18 leap year and 67 ordinary year so)=(18*2+57)
Which is equal to 93 then it will give 2 odd days
So total no of odd days=0+5+2=7 so seven odd days is equal to 1 weak so odd days Is 0
From 1776 January 1 to July 16th 1776
Jan=31 February =29 march =31 April =30 June=31 July=16
So total no of days=198 odd days =2 days
So the day is Tuesday see the formula
What was the day of the week on 16th April 2000
2000=(1999+2000 January to April 16th)
1999=(1600+399)
399=(300+99)
99=24 leap year and 75 ordinary days
So (24*2+75)=123 days there odd days are 4---------------------------1
300 it has 1 odd days---------------------------------2
1600 it has 0 odd days -----------------------------3
2000 January to 16th April
January=31 February=29 march=31 April=16
So 31+29+30+16=107 it has 2 odd days-----------4
Finally form 1,2,3,4 odd days are=4+1+0+2=7
7 odd days become one week so it has 0 odd days so there date is Sunday –Interview important Aptitude Question