A Veteran is anyone who has served, even for a day. They offer to put their lives on the line for their country and their allies, in the hope that someone else does not have to.
The article in the express should have been written by a Veteran. It refers to celebrations - we don't celebrate, we remember. It's also not just a Commonwealth day. A lot of our allies who are not members of the Commonwealth remember this day, especially in the US.
It's not just about the first and second world wars; it's about all wars and conflicts where people have served. Lately, this includes the Falklands, the first Iraq war, Kosovo, and since 9/11, Iraq, Afghanistan, and other parts of the world.