Sentence:  The third day before the <WSD>nones</WSD> of March is March 5th; the third <WSD>nones</WSD> of August is August 3rd; and the third of the <WSD>nones</WSD> of November is November 3rd. 
Meaning of the word marked with <WSD> tags:  The notional first-quarter day of a Roman month, occurring on the 7th day of the four original 31-day months (March, May, Quintilis or July, and October) and on the 5th day of all other months.