I'm assuming that you mean July 27, 1961 and that would be a Thursday. The earliest calendar was the Gregorian calendar which began in 1582.
Thursday, the day of the week
July 27, 1992 was a Monday.
July 27 1948 was on a Tuesday.
July 27, 1951, was a Friday.
July 27 2000 was a Thursday.
27 July 1953 was a Monday.
July 27, 1980, was a Sunday.
July 27 2010 was a Tuesday
July 27 1941 was a Sunday.
July 27 1998 was a Monday.
July 27 1994 was a Wednesday.
July 27 2006 was a Thursday.