Fires when the state of a timer world state UI element changes or becomes available. World State UI elements include PvP, instance, and quest objective information (displayed at the top center of the screen in the default UI) as well as more specific information for "control point" style PvP objectives. Timer world state elements include the countdown between battles in Wintergrasp, the countdown between periods in which the PvP objectives in Terokkar Forest are available, and timers shown for the quests The Light of Dawn and The Battle For The Undercity.