OCG Rulings

• While the effect is applied, both Battle Damage and effect damage is reduced to 0.^[1]

• "One Day of Peace" only zeroes damage that is inflicted to a player. Monsters are still destroyed by Battle Damage calculation.^[1]

• If you activate "One Day of Peace" and apply its effect, then you can activate a second copy of "One Day of Peace" during the same turn.^[2]

References

1. ↑ ^{1.0 1.1} Konami OCG FAQ: Spell Card > One Day of Peace
2. ↑ Konami OCG FAQ: Can you activate a second "One Day of Peace" while applying the first one's effect?