A question to those familiar with the history of the game; when was the last time the rules of chess were changed? I mean the rules of the game itself, not tournament rules etc. Contrary to my belief (I thought that European chess was unchanged throughout centuries) I read that, for example, castling rules were established not that long ago. What was the very last change then?

No expert here, but I think the most recent major changes to the rules were a few hundred years ago (i.e. how the pieces move). Anyone?

Free castling: isn't that where the player could move the k to h8, the rook to e1 for example.

I think that was an obscure holdout and long gone?

Interesting question though. When was the last major change?

I think I remember that the last major changes were in 1492, when pawns were given the ability to move forward two squares on the first move instead of just one, and en pessant was added to deal with that. That's also around the time that castling was added and the queen became so powerful, as it had been a much weaker piece previously. I don't remember where I heard that specific year, but I remember that it was the same year that Columbus reached the Americas, which is why the year stood out to me.

A more minor rules change that I know about is white being given the first move. Apparently, in the 19th century, black sometimes moved first. Because the board's symmetric, that doesn't actually affect game play, so I consider that one minor.

Also, I know the way draws were counted in tournaments has changed along the way, though counting it as half a win has been the most common practice for probably around a century now.

--Fromper

I asked because in Peter Kurzdorfer's "Everything Chess Basics Book" I read that castling rules were established (standardized, unified?) only just within the last 150 years, so not in 15th century!

Castling itself is older, but it was being done in various ways (such as simply swapping King and Rook, as Hoosker mentioned)