TCG Rulings

• You can activate this card during the Damage Step.^[1]

• You can Chain this card to the activation of any of your opponent's Effect Monsters effects, even ones in their hand or Graveyard.^[1]

OCG Rulings

• You can activate "Chivalry" during the Damage Step and during damage calculation.^[2]

References

1. ↑ ^{1.0 1.1} Konami Gameplay FAQ: Duelist Revolution Sneak Peek -- Card Rulings (Version 1.0)
2. ↑ Konami FAQ: Trap Card > Chivalry