What happens to the timestamp of an attached permanent when it is attached to a different object?

When a permanent is attached to a different object, it receives a new timestamp. This is important because the timestamp is used to determine which of two permanents entered the battlefield first, influencing various interactions within the game.

When a permanent such as an Aura or Equipment becomes attached to a different eligible permanent, it is considered to have left its previous attachment and entered a new state of attachment. Consequently, it effectively "starts anew" in this context, thus receiving a new timestamp. This ensures clarity in game mechanics, particularly in scenarios where the order of permanents is critical—such as determining the effects of abilities that rely on the timestamps of the permanents involved.

The other options don't accurately reflect the rules governing timestamps in this context. Retaining the original timestamp or resetting it to zero does not apply to the rules of attachment, as the new context of the attachment alters the state of the permanent. Additionally, stating that the timestamp becomes irrelevant overlooks the fact that it is vital for the game's mechanics moving forward.