On April 21, 10 a.m. to 2 p.m., celebrate conservation success stories at the Smithsonian’s National Zoo in honor of Earth Day. This year’s event features family-friendly activities, hands-on learning opportunities and interactive demonstrations. Zoo hours are 8 a.m. to 5 p.m. Last admittance is 4 p.m. Zoo admission is free; parking is $25. 3001 Connecticut Ave. NW. nationalzoo.si.edu.