For Dieselpunks in the US today, which is Memorial Day, is one that I think probably touches many of us in a way that it might not some.
World War I in many ways gave birth to the Diesel Era. One cannot fully understand the Diesel Era without understanding the role of the Great War. I would highly recommend Tome's excellent article about the Lost Generation in the recent issue of the Gatehouse Gazette.
At the other end of the Diesel Era there's World War II, which provides so much inspiration to Dieselpunk. A war in which the world hung perilously on verge of the abyss of a Dystopian Piecraftian nightmare becoming a reality.
To all who have served, to all who serve today, and especially to those who gave the ultimate sacrifice this is the day that we here in America set aside to collectively say: "Thank you."