Given Today is 20th January 2017, Sunday
In january, we have 31 days
February - 28 days (Non leap year)
March - 31 days
April - 30 days
=> Remaining days => 31 - 20 = 11 in Jan
+ 28 in Feb + 31 in Mar = 11 + 28 + 31 = 70 days
More 20 days to complete 90 days => upto 20th April
Therefore, after 90 days from today i.e, 20th Jan 2017 is 20th Apr 2017.
Now, the day of the week will be
90/7 => Remainder '6'
As the day starts with '0' on sunday
6 => Saturday.
Required day is 20th April, Saturday.
