Unwinding Clock | Magic: The Gathering
Formats Unwinding Clock is Legal in
Official Oracle Text for Unwinding Clock
Official Rulings for Unwinding Clock
6/1/2011 : Some effects, such as the one generated by Rust Tick's ability, state that an artifact doesn't untap during its controller's untap step. These effects won't apply and stop the artifact from untapping during another player's untap step.
6/1/2011 : Even if you control more than one Unwinding Clock, you'll only untap your artifacts once during each other player's untap step.