Mark your calendars, Blackberries, iPhones, iPads, or just write it on your damn hand -- 'cause now it's officially official: MGMT's second album, Congratulations, will release in the U.S. on April 13. MGMT's core duo of Andrew Vanwyngarden and Ben Goldwasser recorded the album at studios in Upstate, NY, Brooklyn, and Malibu, CA, with producer Peter Kember, a.k.a. Sonic Boom of shoegaze pioneers Spaceman 3, and their live band -- Matt Asti (bass), Will Berman (drums), and James Richardson (guitar). Royal Trux frontwoman Jennifer Herrema helped with vocals, while knob-twiddler extraordinaire…