Symbiosis National Aptitude Test SNAP 2019 Paper

We know that year that have same calender have interval of +6 years, +11 years, +11 years.
So, 1981 have same calender year as 1987, 1998, 2009, 2015.
Now, number of days between 1st June 2015 and 1st June 2013 = 365 + 365.
Again, number of odd days in a non-leap year = 1.
∴ Number of odd days from 1st June 2013 to 1st June 2015 = 2.
Hence, 1st June 2015 = 1st June 1981 = Monday.