Strictly speaking, the last time I touched the Appalachian Trail was October 13, 2014, when leaving the "Jersey House". But, that was when we drove over the road crossing on US-206 in Branchville, NJ.
The last time I set foot proper on the AT, though I didn't really know it at the time, was August 15, 2010, while on vacation in Charlottesville, VA. The hike that day was about a 9.5 mile loop, roughly half on the AT and half on other trails in Shenandoah. (The particularly rugged portion of that hike was the side trail, which went down into a valley and back up. The AT, by comparison, was relatively flat!)