HAPPENIN’ OTSEGO for SATURDAY, APRIL 6 Annual Postcard, Book, Ephemera Show and Sale HISTORY CENTER—10 a.m. to 3:30 p.m. “17th Annual Postcard, Book, and Ephemera Show and Sale.” Vendors, auction, 50/50 raffle, and highlights from the upcoming summer exhibition by the Greater Oneonta Historical Society. Free admission. Held in the social room of the Elm Park Methodist Church, 401 Chestnut Street, Oneonta. (607) 432-0960 or visit https://oneontahistory.org/events-programs/ BLOOD DRIVE—10 a.m. to 3 p.m. Hartwick College, 1 Hartwick College Drive, Oneonta. RedCrossBlood.org…