Preceded by a number and indicating, roughly, “… years later.” More so than “later,” “on” provides a retrospective feel, and thus is useful in titles, as in Alan Bennett’s first produced play, the 1968 “Forty Years On.” The two-letter word makes the expression especially tempting for headline writers, and as the tenth anniversary of 9/11/01 approaches, it is ubiquitous. A Google News search for the phrase in headlines yields 424 hits for just the two days Sept. 3 and 4, 2011, from “Bin Laden Wanted a Second Hit, Ten Years On” (Sydney Herald) to “10 Years On: Finally, Smarter Airport Security Screening?” (Wall Street Journal).
A Consummate Teacher: Coach Robinson 50 Years On. (New York Times headline, August 4, 1991)/Though we’ve felt the impact of 9/11, more will yet unfold. Ten years on, it still might be “too soon to tell.” (Sacramento Bee, September 4, 2011)