Today has been one of those days that I'd classify as a "busy day." I got to wondering about what people called a "busy day" in ages past. So, using Google Books, I did a quick survey.
In the Diary and Letters of Madame D'Arbley (London: Henry Colburn, 1842, vol. 2, pp. 225-226), she classified January 3, 1783 as a "busy day." She basically describes a day of going to the grand rehearsal of the opera Cimene.
Somehow I suspect that my ancestors would have said that Madame D'Arbley didn't know what it meant to be busy.
William M. Thomson, a missionary to Syria, described Sept. 14, 1839 as a "busy day". He spoke of the visit of several sheiks to his station. He mentioned that he had been teaching pretty much all day and evening and that several of the sheiks wished to be baptized before returning to the mountains. Two days later, he stated that Sept. 16, 1839 which was the Sabbath was also a "busy day." He said, "After preaching, both in English and Aramaic, and conversing all the vacant time with the Druzes from Hadet, and other places, and expounding Scripture in Aramaic at evening worship, I feel wearied." Later in the paragraph he states that "the work has grown too large for me to attend to." (Report of the American Board of Commissioners for Foreign Missions, Presented at the Thirtieth Annual Meeting , Held in the City of Troy, New-York, Sept. 11-12-13, 1839 (Boston: Crocker & Brewster, 1839), p. 88)
In describing life in the Civil War for the Second Brigade of the Ninth Ohio Cavalry, the record describes General Rousseau as having reached Decatur (Tennessee) on July 9, 1864. Then it says, "Sunday, the tenth, was a busy day in camp; anything but a Sabbath-like stillness prevailed." The rest of the day's entry describes packing up camp, leaving behind things that would create too much baggage, assigning rations to the soldiers, and then marching some 15 miles to Somerville, which was a county seat about 15 miles from Decatur. They arrived there around 9 p.m. (Moore, Frank, ed. The Rebellion Record: A Diary of American Events, with Documents, Narratives, Illustrative Incidents, Poetry, Etc. (New York: D. Van Nostrand, 1868), vol. 11, pp. 160-161)
Most of the other references in the first 50 hits were in literary works.