Explanation : Although 1980 is a leap year, it would not have any
impact on the calculation as the date in the question is
in January month (and before 28th February). Thus, it
is assumed as a normal year. There is a gain of one day
in the next year. However, here, we will do backward
calculation, subtract 1 day from the year 1980. If it was
Saturday, then the same day in the previous year was
to be Friday