A "Headband of Inspired Wisdom +2" adds +2 to your Wisdom score. So a +1 to you Wisdom modifier. The first 24 hours it is worn you get a temporary ability bonus after that it is permanent for as long as you wear it.
Because it is a temporary ability bonus a Cleric doesn't get bonus spells per day from it.
But does it work for his spell save DC? Does the temporary ability bonus from the Headband increase the spell save DC for cleric spells like an "Owl's Wisdom"does?
(an "Owl's Wisdom" only increase the spell save DC not the number of bonus spells)