The BP World of Tennis Yearbook 1980 gave me the idea for this thread.
In Connors' bio at the back of the book, it says 'After slipping behind Borg and Vilas with losing records against both in 1977, Connors had a better year in1978, capturing his third US Open, his first Masters and reaching the final of Wimbledon for the third time in the last four years, a tournament he won in 1974'.
In a way, they seemed to count this Masters as in1978, because it occured in the 1978 calendar year. We count it as the 1977 Masters.
By the way, I used to love that yearbook.