Won on the field
Beat the holder, take the belt. Every other result leaves it exactly where it was.
Ties: holder retains
Standard lineal convention. A tie isn’t a loss, so it isn’t treated like one.
Idle holder, belt carries
A bye, a canceled season, a bowl opt-out — the belt just waits for the next game.
Computed, not researched
Every reign is derived mechanically from the full game record — no editorial judgment per game.