In this lovely paper: https://tom7.org/chess/longest.pdf https://tom7.org/chess/longest.pdf The author points out that: "This rule only applied to games start

In this lovely paper: https://tom7.org/chess/longest.pdf https://tom7.org/chess/longest.pdf The author points out that: "This rule only applied to games started after its introduction, so it is possible that some pre-1561 games are still in progress and may never end."