2004-10-04 : Disharmony works even if the attacker was not tapped to attack.

2004-10-04 : The creature untaps (if it was tapped) before you get control of it.

2008-10-01 : Disharmony can target a creature you control.

2008-10-01 : The current wording explicitly removes the creature from combat. It is no longer an attacking or blocking creature.

2009-10-01 : If you cast Disharmony during an opponent’s turn, you may then block with the creature you gain control of (assuming there’s an attacking creature it can block).

2013-09-20 : If a turn has multiple combat phases, this spell can be cast during any of them as long as it’s before the beginning of that phase’s Declare Blockers Step.