This read-write yes/no setting determines whether this configured time period is actually used during the time span it covers, and the desc notes that when no periods are enabled or none currently cover the clock, the unit falls back to the default WAN link operating mode. It lets an administrator define a schedule entry without immediately activating it, or temporarily suspend one without deleting its configuration. For example, disabling this object for a holiday-hours period keeps that period's time/day settings intact while the unit continues running its default WAN mode instead.